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getpixel(3alleg4) [debian man page]

getpixel(3alleg4)						  Allegro manual						 getpixel(3alleg4)

NAME
getpixel - Reads a pixel from a bitmap. Allegro game programming library. SYNOPSIS
#include <allegro.h> int getpixel(BITMAP *bmp, int x, int y); DESCRIPTION
Reads a pixel from point (x, y) in the bitmap. RETURN VALUE
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. 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(). To extract the individual color components, use the getr() / getg() / getb() / geta() family of functions. SEE ALSO
putpixel(3alleg4), _getpixel(3alleg4), is_inside_bitmap(3alleg4), getr(3alleg4), getg(3alleg4), getb(3alleg4), geta(3alleg4), ex12bit(3alleg4), exalpha(3alleg4), exflame(3alleg4), exlights(3alleg4) Allegro version 4.4.2 getpixel(3alleg4)

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getpixel(3alleg4)						  Allegro manual						 getpixel(3alleg4)

NAME
getpixel - Reads a pixel from a bitmap. Allegro game programming library. SYNOPSIS
#include <allegro.h> int getpixel(BITMAP *bmp, int x, int y); DESCRIPTION
Reads a pixel from point (x, y) in the bitmap. RETURN VALUE
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. 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(). To extract the individual color components, use the getr() / getg() / getb() / geta() family of functions. SEE ALSO
putpixel(3alleg4), _getpixel(3alleg4), is_inside_bitmap(3alleg4), getr(3alleg4), getg(3alleg4), getb(3alleg4), geta(3alleg4), ex12bit(3alleg4), exalpha(3alleg4), exflame(3alleg4), exlights(3alleg4) Allegro version 4.4.2 getpixel(3alleg4)
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