getpixel(3)

💖 getpixel(3) 💖

okay bestie, welcome to the Allegro manual — yes, the game programming library, we're being ✨productive✨ today. this one's a lil function called getpixel and she is so simple it's almost suspicious. let's go 🦋

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🌸 NAME 🌸

getpixel — reads a pixel from a bitmap. that's it. that's the whole job. Allegro game programming library behavior, no cap 💅

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✨ SYNOPSIS ✨

#include <allegro.h>

int getpixel(BITMAP *bmp, int x, int y);

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🎀 DESCRIPTION 🎀

so you give her a point (x, y) and she reads the pixel right there in the bitmap. that's the vibe. one point, one pixel, done. 🌈

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👑 RETURN VALUE 👑

she hands you back the value of that pixel — in the color format of the bitmap, so like, whatever format that bitmap speaks, that's what you get back. 🫶

but if the point lies outside the bitmap (and heads up, she's ignoring the clipping rectangle here, so it's about the actual bitmap bounds), you get -1. periodt.

⚠️ WARNING, and this one's important bestie, don't skip it: -1 is also a totally valid pixel value for pixels in 32-bit bitmaps with an alpha channel — specifically when R,G,B,A are all equal to 255. so you literally cannot use "is it -1?" as a test for whether you're inside the bitmap when you're dealing with those. it will lie to you. it will betray you. 💀

the only reliable predicate in those cases is is_inside_bitmap(). use her. trust her. she's the main character here. 👑

and if you wanna pull the individual color components out of that pixel value, that's the getr() / getg() / getb() / geta() family of functions. they're the girlies for that job. 🧚

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💜 SEE ALSO 💜

• putpixel(3)
• _getpixel(3)
• is_inside_bitmap(3)
• getr(3)
• getg(3)
• getb(3)
• geta(3)
• ex12bit(3)
• exalpha(3)
• exflame(3)
• exlights(3)

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and that's the whole page, bestie!! 🍓 this lil gem came to you courtesy of Allegro, version 4.4.3 — go read a pixel, or don't, either way you understood the assignment. mwah 💅✨🎀