1getpixel(3)                     Allegro manual                     getpixel(3)
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NAME

6       getpixel  -  Reads  a  pixel  from  a  bitmap. Allegro game programming
7       library.
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SYNOPSIS

10       #include <allegro.h>
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13       int getpixel(BITMAP *bmp, int x, int y);
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DESCRIPTION

16       Reads a pixel from point (x, y) in the bitmap.
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RETURN VALUE

19       Returns -1 if the point lies outside the bitmap (ignoring the  clipping
20       rectangle), otherwise the value of the pixel in the color format of the
21       bitmap.
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23       Warning: -1 is also a valid value for pixels contained in  32-bit  bit‐
24       maps  with  alpha  channel  (when  R,G,B,A are all equal to 255) so you
25       can't use the test against -1 as a predicate for such bitmaps. In  this
26       cases, the only reliable predicate is is_inside_bitmap().
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28       To  extract  the individual color components, use the getr() / getg() /
29       getb() / geta() family of functions.
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SEE ALSO

33       putpixel(3),  _getpixel(3),  is_inside_bitmap(3),   getr(3),   getg(3),
34       getb(3), geta(3), ex12bit(3), exalpha(3), exflame(3), exlights(3)
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38Allegro                          version 4.4.3                     getpixel(3)
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