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Allegro Manual: Drawing primitives
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<h1><a name="Drawing primitives">Drawing primitives</a></h1>
<ul>
<li><a href="#_getpixel">_getpixel</a> — Faster specific version of getpixel().
<li><a href="#_getpixel15">_getpixel15</a> — Faster specific version of getpixel().
<li><a href="#_getpixel16">_getpixel16</a> — Faster specific version of getpixel().
<li><a href="#_getpixel24">_getpixel24</a> — Faster specific version of getpixel().
<li><a href="#_getpixel32">_getpixel32</a> — Faster specific version of getpixel().
<li><a href="#_putpixel">_putpixel</a> — Faster specific version of putpixel().
<li><a href="#_putpixel15">_putpixel15</a> — Faster specific version of putpixel().
<li><a href="#_putpixel16">_putpixel16</a> — Faster specific version of putpixel().
<li><a href="#_putpixel24">_putpixel24</a> — Faster specific version of putpixel().
<li><a href="#_putpixel32">_putpixel32</a> — Faster specific version of putpixel().
<li><a href="#arc">arc</a> — Draws a circular arc.
<li><a href="#calc_spline">calc_spline</a> — Calculates a series of values along a Bezier spline.
<li><a href="#circle">circle</a> — Draws a circle.
<li><a href="#circlefill">circlefill</a> — Draws a filled circle.
<li><a href="#clear_bitmap">clear_bitmap</a> — Clears the bitmap to color 0.
<li><a href="#clear_to_color">clear_to_color</a> — Clears the bitmap to the specified color.
<li><a href="#do_arc">do_arc</a> — Calculates all the points in a circular arc.
<li><a href="#do_circle">do_circle</a> — Calculates all the points in a circle.
<li><a href="#do_ellipse">do_ellipse</a> — Calculates all the points in an ellipse.
<li><a href="#do_line">do_line</a> — Calculates all the points along a line.
<li><a href="#ellipse">ellipse</a> — Draws an ellipse.
<li><a href="#ellipsefill">ellipsefill</a> — Draws a filled ellipse.
<li><a href="#fastline">fastline</a> — Faster version of line().
<li><a href="#floodfill">floodfill</a> — Floodfills an enclosed area.
<li><a href="#getpixel">getpixel</a> — Reads a pixel from a bitmap.
<li><a href="#hline">hline</a> — Draws a horizontal line onto the bitmap.
<li><a href="#line">line</a> — Draws a line onto the bitmap.
<li><a href="#polygon">polygon</a> — Draws a filled polygon.
<li><a href="#putpixel">putpixel</a> — Writes a pixel into a bitmap.
<li><a href="#rect">rect</a> — Draws an outline rectangle.
<li><a href="#rectfill">rectfill</a> — Draws a solid filled rectangle.
<li><a href="#spline">spline</a> — Draws a Bezier spline using four control points.
<li><a href="#triangle">triangle</a> — Draws a filled triangle.
<li><a href="#vline">vline</a> — Draws a vertical line onto the bitmap.
</ul>
<p>
Except for _putpixel(), all these routines are affected by the current
drawing mode and the clipping rectangle of the destination bitmap. Unless
specified otherwise, all coordinates for drawing operations are inclusive,
and they, as well as lengths, are specified in pixel units.
<p><br>
<div class="al-api"><b>void <a name="clear_bitmap">clear_bitmap</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bitmap);</b></div><br>
Clears the bitmap to color 0.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#clear_to_color" title="Clears the bitmap to the specified color.">clear_to_color</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="clear_to_color">clear_to_color</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bitmap, int color);</b></div><br>
Clears the bitmap to the specified color. Example:
<blockquote class="code"><pre>
/* Clear the <a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a> to red. */
<a href="#clear_to_color" class="autotype" title="Clears the bitmap to the specified color.">clear_to_color</a>(bmp, <a href="alleg012.html#makecol" class="autotype" title="Converts an RGB value into the current pixel format.">makecol</a>(255, 0, 0));</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#clear_bitmap" title="Clears the bitmap to color 0.">clear_bitmap</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="putpixel">putpixel</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
Writes a pixel to the specified position in the bitmap, using the current
drawing mode and the bitmap's clipping rectangle. Example:
<blockquote class="code"><pre>
<a href="#putpixel" class="autotype" title="Writes a pixel into a bitmap.">putpixel</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, 10, 30, some_color);</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#getpixel" title="Reads a pixel from a bitmap.">getpixel</a>,
<a class="xref" href="#_putpixel" title="Faster specific version of putpixel().">_putpixel</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex12bit" title="How to fake a 12-bit truecolor mode on an 8-bit card.">ex12bit</a>,
<a class="eref" href="alleg046.html#exalpha" title="Creating and using 32 bit RGBA sprites.">exalpha</a>,
<a class="eref" href="alleg046.html#exflame" title="How to write directly to video memory improving performance.">exflame</a>,
<a class="eref" href="alleg046.html#exjoy" title="Detecting, calibrating and using joystick input.">exjoy</a>,
<a class="eref" href="alleg046.html#exstars" title="3d starfield and lightsourced spaceship.">exstars</a>,
<a class="eref" href="alleg046.html#exswitch" title="Controlling the console switch mode for background running.">exswitch</a>.</blockquote>
<div class="al-api"><b>void <a name="_putpixel">_putpixel</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
<div class="al-api-cont"><b>void <a name="_putpixel15">_putpixel15</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
<div class="al-api-cont"><b>void <a name="_putpixel16">_putpixel16</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
<div class="al-api-cont"><b>void <a name="_putpixel24">_putpixel24</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
<div class="al-api-cont"><b>void <a name="_putpixel32">_putpixel32</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
Like the regular putpixel(), but much faster because they are implemented
as an inline assembler functions for specific color depths. These won't
work in mode-X graphics modes, don't perform any clipping (they will
crash if you try to draw outside the bitmap!), and ignore the drawing
mode.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#putpixel" title="Writes a pixel into a bitmap.">putpixel</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<div class="al-api"><b>int <a name="getpixel">getpixel</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
Reads a pixel from point (x, y) in the bitmap.
<p><b>Return value:</b>
Returns -1 if the point lies outside the bitmap (ignoring the clipping
rectangle), otherwise the value of the pixel in the color format of the
bitmap.
<p>
Warning: -1 is also a valid value for pixels contained in 32-bit bitmaps
with alpha channel (when R,G,B,A are all equal to 255) so you can't use
the test against -1 as a predicate for such bitmaps. In this cases, the
only reliable predicate is is_inside_bitmap().
<p>
To extract the individual color components, use the getr() / getg() /
getb() / geta() family of functions.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#putpixel" title="Writes a pixel into a bitmap.">putpixel</a>,
<a class="xref" href="#_getpixel" title="Faster specific version of getpixel().">_getpixel</a>,
<a class="xref" href="alleg009.html#is_inside_bitmap" title="Tells if a point is inside a bitmap.">is_inside_bitmap</a>,
<a class="xref" href="alleg012.html#getr" title="Extract a color component from the current pixel format.">getr</a>,
<a class="xref" href="alleg012.html#getg" title="Extract a color component from the current pixel format.">getg</a>,
<a class="xref" href="alleg012.html#getb" title="Extract a color component from the current pixel format.">getb</a>,
<a class="xref" href="alleg012.html#geta" title="Extract a color component from the current pixel format.">geta</a>,
<a class="xref" href="alleg012.html#Truecolor pixel formats" title="">Truecolor pixel formats</a>,
<a class="xref" href="alleg011.html#Palette routines" title="">Palette routines</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex12bit" title="How to fake a 12-bit truecolor mode on an 8-bit card.">ex12bit</a>,
<a class="eref" href="alleg046.html#exalpha" title="Creating and using 32 bit RGBA sprites.">exalpha</a>,
<a class="eref" href="alleg046.html#exflame" title="How to write directly to video memory improving performance.">exflame</a>,
<a class="eref" href="alleg046.html#exlights" title="One way to do colored lighting effects in a hicolor video mode.">exlights</a>.</blockquote>
<div class="al-api"><b>int <a name="_getpixel">_getpixel</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
<div class="al-api-cont"><b>int <a name="_getpixel15">_getpixel15</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
<div class="al-api-cont"><b>int <a name="_getpixel16">_getpixel16</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
<div class="al-api-cont"><b>int <a name="_getpixel24">_getpixel24</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
<div class="al-api-cont"><b>int <a name="_getpixel32">_getpixel32</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y);</b></div><br>
Faster inline versions of getpixel() for specific color depths. These
won't work in mode-X, and don't do any clipping, so you must make sure
the point lies inside the bitmap.
<p><b>Return value:</b>
Returns the value of the pixel in the color format you specified.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#getpixel" title="Reads a pixel from a bitmap.">getpixel</a>.</blockquote>
<div class="al-api"><b>void <a name="vline">vline</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y1, int y2, int color);</b></div><br>
Draws a vertical line onto the bitmap, from point (x, y1) to (x, y2).
<p>
Note: vline() is implemented as an alias to another function.
See ALLEGRO_NO_VHLINE_ALIAS in the `Differences between platforms'
section for details.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#hline" title="Draws a horizontal line onto the bitmap.">hline</a>,
<a class="xref" href="#line" title="Draws a line onto the bitmap.">line</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>,
<a class="xref" href="alleg042.html#Differences between platforms" title="">Differences between platforms</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#exrgbhsv" title="RGB <-> HSV color space conversions.">exrgbhsv</a>,
<a class="eref" href="alleg046.html#exscroll" title="Mode-X hardware scrolling and split screens.">exscroll</a>,
<a class="eref" href="alleg046.html#extruec" title="Truecolor pixel format conversions.">extruec</a>.</blockquote>
<div class="al-api"><b>void <a name="hline">hline</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, int y, int x2, int color);</b></div><br>
Draws a horizontal line onto the bitmap, from point (x1, y) to (x2, y).
<p>
Note: hline() is implemented as an alias to another function.
See ALLEGRO_NO_VHLINE_ALIAS in the `Differences between platforms'
section for details.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#vline" title="Draws a vertical line onto the bitmap.">vline</a>,
<a class="xref" href="#line" title="Draws a line onto the bitmap.">line</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>,
<a class="xref" href="alleg042.html#Differences between platforms" title="">Differences between platforms</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#exsprite" title="Datafiles access and sprite animation.">exsprite</a>.</blockquote>
<div class="al-api"><b>void <a name="do_line">do_line</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, y1, x2, y2, int d,
void (*proc)(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d));</b></div><br>
Calculates all the points along a line from point (x1, y1) to (x2, y2),
calling the supplied function for each one. This will be passed a copy of
the bmp parameter, the x and y position, and a copy of the d parameter,
so it is suitable for use with putpixel(). Example:
<blockquote class="code"><pre>
void draw_dust_particle(<a href="alleg001.html#BITMAP" class="autotype" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d)
{
...
}
<a href="#do_line" class="autotype" title="Calculates all the points along a line.">do_line</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, 0, 0, <a href="alleg009.html#SCREEN_W" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_W</a>-1, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>-2,
dust_strength, draw_dust_particle);</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#do_circle" title="Calculates all the points in a circle.">do_circle</a>,
<a class="xref" href="#do_ellipse" title="Calculates all the points in an ellipse.">do_ellipse</a>,
<a class="xref" href="#do_arc" title="Calculates all the points in a circular arc.">do_arc</a>,
<a class="xref" href="#line" title="Draws a line onto the bitmap.">line</a>.</blockquote>
<div class="al-api"><b>void <a name="line">line</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, int y1, int x2, int y2, int color);</b></div><br>
Draws a line onto the bitmap, from point (x1, y1) to (x2, y2).
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#fastline" title="Faster version of line().">fastline</a>,
<a class="xref" href="#hline" title="Draws a horizontal line onto the bitmap.">hline</a>,
<a class="xref" href="#vline" title="Draws a vertical line onto the bitmap.">vline</a>,
<a class="xref" href="#do_line" title="Calculates all the points along a line.">do_line</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="fastline">fastline</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, int y1, int x2, int y2, int color);</b></div><br>
Faster version of the previous function. Note that pixel correctness is
not guaranteed for this function.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#line" title="Draws a line onto the bitmap.">line</a>,
<a class="xref" href="#hline" title="Draws a horizontal line onto the bitmap.">hline</a>,
<a class="xref" href="#vline" title="Draws a vertical line onto the bitmap.">vline</a>,
<a class="xref" href="#do_line" title="Calculates all the points along a line.">do_line</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#Available Allegro examples" title="">Available Allegro examples</a>.</blockquote>
<div class="al-api"><b>void <a name="triangle">triangle</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, y1, x2, y2, x3, y3, int color);</b></div><br>
Draws a filled triangle between the three points.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#polygon" title="Draws a filled polygon.">polygon</a>,
<a class="xref" href="alleg019.html#triangle3d" title="Draws a 3d triangle onto the specified bitmap.">triangle3d</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex3buf" title="Mode-X triple buffering and retrace interrupt simulation.">ex3buf</a>,
<a class="eref" href="alleg046.html#exstars" title="3d starfield and lightsourced spaceship.">exstars</a>,
<a class="eref" href="alleg046.html#exupdate" title="Supporting different screen update methods in a single program.">exupdate</a>.</blockquote>
<div class="al-api"><b>void <a name="polygon">polygon</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int vertices, const int *points, int color);</b></div><br>
Draws a filled polygon with an arbitrary number of corners. Pass the
number of vertices and an array containing a series of x, y points (a
total of vertices*2 values). Example:
<blockquote class="code"><pre>
int points[12] = { 50, 50, 100, 100, 100, 150,
50, 200, 0, 150, 0, 100 };
...
<a href="#clear_to_color" class="autotype" title="Clears the bitmap to the specified color.">clear_to_color</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, <a href="alleg012.html#makecol" class="autotype" title="Converts an RGB value into the current pixel format.">makecol</a>(255, 255, 255));
<a href="#polygon" class="autotype" title="Draws a filled polygon.">polygon</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, 6, points, <a href="alleg012.html#makecol" class="autotype" title="Converts an RGB value into the current pixel format.">makecol</a>(0, 0, 0));</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#triangle" title="Draws a filled triangle.">triangle</a>,
<a class="xref" href="alleg019.html#polygon3d" title="Draws a 3d polygon onto the specified bitmap.">polygon3d</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#excamera" title="Viewing a 3d world from an arbitrary camera position.">excamera</a>.</blockquote>
<div class="al-api"><b>void <a name="rect">rect</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, int y1, int x2, int y2, int color);</b></div><br>
Draws an outline rectangle with the two points as its opposite corners.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#rectfill" title="Draws a solid filled rectangle.">rectfill</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex3d" title="3d 'bouncy cubes' demo.">ex3d</a>,
<a class="eref" href="alleg046.html#excamera" title="Viewing a 3d world from an arbitrary camera position.">excamera</a>.</blockquote>
<div class="al-api"><b>void <a name="rectfill">rectfill</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x1, int y1, int x2, int y2, int color);</b></div><br>
Draws a solid, filled rectangle with the two points as its opposite
corners.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#rect" title="Draws an outline rectangle.">rect</a>,
<a class="xref" href="#clear_bitmap" title="Clears the bitmap to color 0.">clear_bitmap</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#exalpha" title="Creating and using 32 bit RGBA sprites.">exalpha</a>,
<a class="eref" href="alleg046.html#excolmap" title="Creating graphical effects with color mapping tables.">excolmap</a>,
<a class="eref" href="alleg046.html#exkeys" title="How to get input from the keyboard in different ways.">exkeys</a>,
<a class="eref" href="alleg046.html#exmidi" title="Playing MIDI music.">exmidi</a>,
<a class="eref" href="alleg046.html#expat" title="Using patterned drawing modes and sub-bitmaps.">expat</a>,
<a class="eref" href="alleg046.html#exscroll" title="Mode-X hardware scrolling and split screens.">exscroll</a>,
<a class="eref" href="alleg046.html#exsprite" title="Datafiles access and sprite animation.">exsprite</a>,
<a class="eref" href="alleg046.html#exstars" title="3d starfield and lightsourced spaceship.">exstars</a>,
<a class="eref" href="alleg046.html#exswitch" title="Controlling the console switch mode for background running.">exswitch</a>,
<a class="eref" href="alleg046.html#extrans" title="Lighting and translucency effects.">extrans</a>.</blockquote>
<div class="al-api"><b>void <a name="do_circle">do_circle</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int radius, int d,
void (*proc)(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d));</b></div><br>
Calculates all the points in a circle around point (x, y) with radius r,
calling the supplied function for each one. This will be passed a copy of
the bmp parameter, the x and y position, and a copy of the d parameter,
so it is suitable for use with putpixel(). Example:
<blockquote class="code"><pre>
void draw_explosion_ring(<a href="alleg001.html#BITMAP" class="autotype" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d)
{
...
}
<a href="#do_circle" class="autotype" title="Calculates all the points in a circle.">do_circle</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, <a href="alleg009.html#SCREEN_W" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_W</a>/2, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/2,
<a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/16, flame_color,
draw_explosion_ring);</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#do_ellipse" title="Calculates all the points in an ellipse.">do_ellipse</a>,
<a class="xref" href="#do_arc" title="Calculates all the points in a circular arc.">do_arc</a>,
<a class="xref" href="#do_line" title="Calculates all the points along a line.">do_line</a>,
<a class="xref" href="#circle" title="Draws a circle.">circle</a>,
<a class="xref" href="#circlefill" title="Draws a filled circle.">circlefill</a>.</blockquote>
<div class="al-api"><b>void <a name="circle">circle</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int radius, int color);</b></div><br>
Draws a circle with the specified centre and radius.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#ellipse" title="Draws an ellipse.">ellipse</a>,
<a class="xref" href="#arc" title="Draws a circular arc.">arc</a>,
<a class="xref" href="#circlefill" title="Draws a filled circle.">circlefill</a>,
<a class="xref" href="#do_circle" title="Calculates all the points in a circle.">do_circle</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex12bit" title="How to fake a 12-bit truecolor mode on an 8-bit card.">ex12bit</a>,
<a class="eref" href="alleg046.html#exblend" title="Using translucency in truecolor modes.">exblend</a>,
<a class="eref" href="alleg046.html#excustom" title="Creating custom GUI objects.">excustom</a>,
<a class="eref" href="alleg046.html#exjoy" title="Detecting, calibrating and using joystick input.">exjoy</a>,
<a class="eref" href="alleg046.html#exmem" title="Drawing onto memory bitmaps and then blitting them to the screen.">exmem</a>,
<a class="eref" href="alleg046.html#exmouse" title="Getting input from the mouse.">exmouse</a>,
<a class="eref" href="alleg046.html#exquat" title="A comparison between Euler angles and quaternions.">exquat</a>,
<a class="eref" href="alleg046.html#exsprite" title="Datafiles access and sprite animation.">exsprite</a>.</blockquote>
<div class="al-api"><b>void <a name="circlefill">circlefill</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int radius, int color);</b></div><br>
Draws a filled circle with the specified centre and radius.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#ellipsefill" title="Draws a filled ellipse.">ellipsefill</a>,
<a class="xref" href="#circle" title="Draws a circle.">circle</a>,
<a class="xref" href="#do_circle" title="Calculates all the points in a circle.">do_circle</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#excolmap" title="Creating graphical effects with color mapping tables.">excolmap</a>,
<a class="eref" href="alleg046.html#excustom" title="Creating custom GUI objects.">excustom</a>,
<a class="eref" href="alleg046.html#exdbuf" title="How to use double buffering to avoid flicker.">exdbuf</a>,
<a class="eref" href="alleg046.html#exflip" title="Comparison of double buffering and page flipping.">exflip</a>,
<a class="eref" href="alleg046.html#exlights" title="One way to do colored lighting effects in a hicolor video mode.">exlights</a>,
<a class="eref" href="alleg046.html#expal" title="Palette effects and color cycling.">expal</a>,
<a class="eref" href="alleg046.html#exspline" title="Constructing smooth movement paths from spline curves.">exspline</a>,
<a class="eref" href="alleg046.html#extrans" title="Lighting and translucency effects.">extrans</a>.</blockquote>
<div class="al-api"><b>void <a name="do_ellipse">do_ellipse</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int rx, ry, int d,
void (*proc)(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d));</b></div><br>
Calculates all the points in an ellipse around point (x, y) with radius
rx and ry, calling the supplied function for each one. This will be
passed a copy of the bmp parameter, the x and y position, and a copy of
the d parameter, so it is suitable for use with putpixel(). Example:
<blockquote class="code"><pre>
void draw_explosion_ring(<a href="alleg001.html#BITMAP" class="autotype" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d)
{
...
}
<a href="#do_ellipse" class="autotype" title="Calculates all the points in an ellipse.">do_ellipse</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, <a href="alleg009.html#SCREEN_W" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_W</a>/2, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/2,
<a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/16, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/32, flame_color,
draw_explosion_ring);</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#do_circle" title="Calculates all the points in a circle.">do_circle</a>,
<a class="xref" href="#do_arc" title="Calculates all the points in a circular arc.">do_arc</a>,
<a class="xref" href="#do_line" title="Calculates all the points along a line.">do_line</a>,
<a class="xref" href="#ellipse" title="Draws an ellipse.">ellipse</a>,
<a class="xref" href="#ellipsefill" title="Draws a filled ellipse.">ellipsefill</a>.</blockquote>
<div class="al-api"><b>void <a name="ellipse">ellipse</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int rx, int ry, int color);</b></div><br>
Draws an ellipse with the specified centre and radius.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#circle" title="Draws a circle.">circle</a>,
<a class="xref" href="#arc" title="Draws a circular arc.">arc</a>,
<a class="xref" href="#ellipsefill" title="Draws a filled ellipse.">ellipsefill</a>,
<a class="xref" href="#do_ellipse" title="Calculates all the points in an ellipse.">do_ellipse</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<div class="al-api"><b>void <a name="ellipsefill">ellipsefill</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int rx, int ry, int color);</b></div><br>
Draws a filled ellipse with the specified centre and radius.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#circlefill" title="Draws a filled circle.">circlefill</a>,
<a class="xref" href="#ellipse" title="Draws an ellipse.">ellipse</a>,
<a class="xref" href="#do_ellipse" title="Calculates all the points in an ellipse.">do_ellipse</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#ex12bit" title="How to fake a 12-bit truecolor mode on an 8-bit card.">ex12bit</a>.</blockquote>
<div class="al-api"><b>void <a name="do_arc">do_arc</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, <a class="autotype" href="alleg001.html#fixed" title="Fixed point integer to replace floats.">fixed</a> a1, <a class="autotype" href="alleg001.html#fixed" title="Fixed point integer to replace floats.">fixed</a> a2, int r, int d,
void (*proc)(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d));</b></div><br>
Calculates all the points in a circular arc around point (x, y) with
radius r, calling the supplied function for each one. This will be passed
a copy of the bmp parameter, the x and y position, and a copy of the d
parameter, so it is suitable for use with putpixel(). The arc will be
plotted in an anticlockwise direction starting from the angle a1 and
ending when it reaches a2. These values are specified in 16.16 fixed
point format, with 256 equal to a full circle, 64 a right angle, etc.
Zero is to the right of the centre point, and larger values rotate
anticlockwise from there. Example:
<blockquote class="code"><pre>
void draw_explosion_ring(<a href="alleg001.html#BITMAP" class="autotype" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int d)
{
...
}
<a href="#do_arc" class="autotype" title="Calculates all the points in a circular arc.">do_arc</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, <a href="alleg009.html#SCREEN_W" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_W</a>/2, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/2,
<a href="alleg032.html#itofix" class="autotype" title="Converts an integer to fixed point.">itofix</a>(-21), <a href="alleg032.html#itofix" class="autotype" title="Converts an integer to fixed point.">itofix</a>(43), 50, flame_color,
draw_explosion_ring);</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#do_circle" title="Calculates all the points in a circle.">do_circle</a>,
<a class="xref" href="#do_ellipse" title="Calculates all the points in an ellipse.">do_ellipse</a>,
<a class="xref" href="#do_line" title="Calculates all the points along a line.">do_line</a>,
<a class="xref" href="#arc" title="Draws a circular arc.">arc</a>.</blockquote>
<div class="al-api"><b>void <a name="arc">arc</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, y, <a class="autotype" href="alleg001.html#fixed" title="Fixed point integer to replace floats.">fixed</a> ang1, ang2, int r, int color);</b></div><br>
Draws a circular arc with centre x, y and radius r, in an anticlockwise
direction starting from the angle a1 and ending when it reaches a2. These
values are specified in 16.16 fixed point format, with 256 equal to a
full circle, 64 a right angle, etc. Zero is to the right of the centre
point, and larger values rotate anticlockwise from there. Example:
<blockquote class="code"><pre>
/* Draw a black <a href="#arc" class="autotype" title="Draws a circular arc.">arc</a> from 4 to 1 o'clock. */
<a href="#arc" class="autotype" title="Draws a circular arc.">arc</a>(<a href="alleg009.html#screen" class="autotype" title="Global pointer to the screen hardware video memory.">screen</a>, <a href="alleg009.html#SCREEN_W" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_W</a>/2, <a href="alleg009.html#SCREEN_H" class="autotype" title="Global define to obtain the size of the screen.">SCREEN_H</a>/2,
<a href="alleg032.html#itofix" class="autotype" title="Converts an integer to fixed point.">itofix</a>(-21), <a href="alleg032.html#itofix" class="autotype" title="Converts an integer to fixed point.">itofix</a>(43), 50, <a href="alleg012.html#makecol" class="autotype" title="Converts an RGB value into the current pixel format.">makecol</a>(0, 0, 0));</pre></blockquote>
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#circle" title="Draws a circle.">circle</a>,
<a class="xref" href="#ellipse" title="Draws an ellipse.">ellipse</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<div class="al-api"><b>void <a name="calc_spline">calc_spline</a>(const int points[8], int npts, int *x, int *y);</b></div><br>
Calculates a series of npts values along a Bezier spline, storing them in
the output x and y arrays. The Bezier curve is specified by the four x/y
control points in the points array: points[0] and points[1] contain the
coordinates of the first control point, points[2] and points[3] are the
second point, etc. Control points 0 and 3 are the ends of the spline, and
points 1 and 2 are guides. The curve probably won't pass through points 1
and 2, but they affect the shape of the curve between points 0 and 3 (the
lines p0-p1 and p2-p3 are tangents to the spline). The easiest way to
think of it is that the curve starts at p0, heading in the direction of
p1, but curves round so that it arrives at p3 from the direction of p2.
In addition to their role as graphics primitives, spline curves can be
useful for constructing smooth paths around a series of control points,
as in exspline.c.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#spline" title="Draws a Bezier spline using four control points.">spline</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#exspline" title="Constructing smooth movement paths from spline curves.">exspline</a>.</blockquote>
<div class="al-api"><b>void <a name="spline">spline</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, const int points[8], int color);</b></div><br>
Draws a Bezier spline using the four control points specified in the
points array. Read the description of calc_spline() for information on
how to build the points array.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="#calc_spline" title="Calculates a series of values along a Bezier spline.">calc_spline</a>,
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
<blockquote class="eref"><em><b>Examples using this:</b></em>
<a class="eref" href="alleg046.html#exspline" title="Constructing smooth movement paths from spline curves.">exspline</a>.</blockquote>
<div class="al-api"><b>void <a name="floodfill">floodfill</a>(<a class="autotype" href="alleg001.html#BITMAP" title="Stores the contents of a bitmap.">BITMAP</a> *bmp, int x, int y, int color);</b></div><br>
Floodfills an enclosed area, starting at point (x, y), with the specified
color.
<blockquote class="xref"><em><b>See also:</b></em>
<a class="xref" href="alleg020.html#drawing_mode" title="Sets the graphics drawing mode.">drawing_mode</a>,
<a class="xref" href="alleg012.html#makecol" title="Converts an RGB value into the current pixel format.">makecol</a>.</blockquote>
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