SDL_PremultiplyAlpha(3)

💅 SDL_PremultiplyAlpha(3) 💅

okay bestie, welcome to the SDL3 FUNCTIONS section of the manual, and today's main character is SDL_PremultiplyAlpha. she premultiplies. she's iconic. let's get into it 🫶

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✨ NAME ✨

SDL_PremultiplyAlpha — Premultiply the alpha on a block of pixels. that's it, that's the whole job, and she does it flawlessly 💖

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🌸 SYNOPSIS 🌸

#include <SDL3/SDL_surface.h>

bool SDL_PremultiplyAlpha(int width, int height, SDL_PixelFormat src_format, const void *src, int src_pitch, SDL_PixelFormat dst_format, void *dst, int dst_pitch, bool linear);

like, look at that signature. it's giving eight arguments and a dream ✨

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🦋 DESCRIPTION 🦋

so here's the tea: this is safe to use with src == dst, but not for other overlapping areas. that's the whole description, no notes 👑

⚠️ bestie please read that again. same pointer? fine. other overlapping areas? NOT fine. do not do it. i'm serious. 🙈

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🎀 FUNCTION PARAMETERS 🎀

• width — the width of the block to convert, in pixels. how wide is the vibe? this wide 📏
• height — the height of the block to convert, in pixels. and how tall? this tall 💅
• src_format — an SDL_PixelFormat value of the src pixels format. tell her what the source pixels are serving 🌈
• src — a pointer to the source pixels. the original, the blueprint, the blueprint that ate 🔥
• src_pitch — the pitch of the source pixels, in bytes. yes, bytes. not pixels. bytes. iykyk ⭐
• dst_format — an SDL_PixelFormat value of the dst pixels format. and what's the destination serving? 👑
• dst — a pointer to be filled in with premultiplied pixel data. she gets filled in, periodt 🍓
• dst_pitch — the pitch of the destination pixels, in bytes. again, bytes bestie, don't come at me with pixels 💀
• linear — true to convert from sRGB to linear space for the alpha multiplication, false to do multiplication in sRGB space. pick your lane, both are valid 🧚

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💜 RETURN VALUE 💜

Returns true on success or false on failure; call SDL_GetError() for more information. so if she says false? don't spiral. just call SDL_GetError() and she'll tell you exactly what went wrong 😭

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🌟 THREAD SAFETY 🌟

okay listen up, this one matters:

• The same destination pixels should not be used from two threads at once. sharing is caring but not here 🙅
• It is safe to use the same source pixels from multiple threads. read-only girlies stay winning 💖

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🌈 AVAILABILITY 🌈

This function is available since SDL 3.2.0. so if you're on something older, it's not her fault, she literally wasn't born yet 💅

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and that's the whole page bestie, you ate it, no crumbs 🫶✨

Simple Directmedia Layer made this, we're all living in SDL 3.4.18 era, and this page is SDL_PremultiplyAlpha(3) — go premultiply something responsibly, ily, bye 👑💖