libobs: Add gs_save_png_file - #777
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Lets callers without Qt (obs-studio-node's screenshot IPC) save a PNG using libobs' existing FFmpeg encoder instead of vendoring an image writer. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Copilot review overview
🟡 Changes recommended
Integer overflow and narrowing can bypass input validation and pass invalid dimensions or strides to FFmpeg.
Review effort: Balanced
Findings: 1
What changed in this PR
Adds PNG encoding to libobs using FFmpeg, enabling consumers to save texture data without bundling another encoder.
Changes:
- Exports
gs_save_png_file. - Supports RGBA, BGRA, BGRX, padded row pitches, and UTF-8 paths.
| File | Description |
|---|---|
libobs/graphics/graphics.h |
Declares the PNG-saving API. |
libobs/graphics/graphics-ffmpeg.c |
Implements validation, conversion, encoding, writing, and cleanup. |
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cx * 4 could wrap in uint32_t and bypass the pitch check, and values above INT_MAX were narrowed into invalid FFmpeg arguments. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
A failure after opening the destination unlinked it even when it already existed. Writing to <file>.tmp and replacing on success leaves an existing file untouched on failure. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
A direct write is enough for screenshots: "wb" already truncates an existing destination, so removing the partial file on failure loses nothing. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Problem: obs-studio-node needs to write a screenshot PNG (streamlabs/obs-studio-node#1786). libobs can decode images but not write them, so that PR vendors stb_image_write.
Change: export
gs_save_png_file(file, data, format, cx, cy, linesize)next togs_create_texture_file_data, encoding with the FFmpeg PNG encoder libobs already links. Accepts RGBA/BGRA/BGRX (BGRX -> opaque), honours row pitch, writes viaos_fopenfor UTF-8 paths, and removes a partial file only if it created it.Effect: no behaviour change for existing code; osn can drop stb once this ships.
Testing:
cmake --build build_x64 --config RelWithDebInfo --target libobs(Windows x64): 0 warnings/errorsgs_create_texture_file_datawith padded pitch, 6 invalid-arg rejections, non-ASCII filename, existing file preserved on rejected call -- 11/11 pass🤖 Generated with Claude Code