webp-format

name	webp-format
description	Use this skill when implementing, integrating, or reviewing WebP read/write C code in wlframe, especially libwebp-based parsing and generation in image, buffer, or related modules. Best for RIFF/WebP container handling, lossy and lossless decode or encode flows, alpha and extended feature handling, and wlframe-style ownership and cleanup review.

WebP Format & libwebp Integration Skill (wlframe/C Style)

When to Apply

Use this skill when implementing, integrating, or reviewing WebP read/write C code in wlframe, especially in image/, buffer/, or related modules, or when using libwebp for WebP parsing/generation.

WebP Format Essentials

• WebP is a modern image format supporting lossy and lossless compression, alpha, animation.
• File is RIFF-based, starts with 'RIFF' and 'WEBP' signatures.
• Supports VP8 (lossy), VP8L (lossless), VP8X (extended), alpha, ICC profile, EXIF, XMP.

libwebp Integration & API Design

• Use official libwebp (https://github.com/webmproject/libwebp).
• Typical workflow:
  1. Use WebPDecode* or WebPEncode* APIs for decoding/encoding.
  2. Set up input/output (file or memory).
  3. Convert pixel data to/from wlframe's internal format as needed.
  4. Release all allocated resources.
• API prefix: wlf_webp_. Use init/create and finish/destroy patterns.
• Struct layout: hot fields first, group pointers/handles/flags, hide implementation details via impl pointer.

Example API Design

struct wlf_webp_image {
	uint32_t width, height;
	uint8_t *pixels;
	int stride;
	int format; // e.g., WLF_PIXEL_FORMAT_RGBA8
	void *impl; // internal state (opaque)
};

bool wlf_webp_load(struct wlf_webp_image *out, const char *path);
bool wlf_webp_save(const struct wlf_webp_image *img, const char *path);
void wlf_webp_finish(struct wlf_webp_image *img);

Best Practices

• Check all allocation, I/O, and libwebp API return values.
• Release resources in strict reverse order of allocation.
• Separate headers and implementation; expose only necessary API.
• Reference image/, buffer/ modules for style and error handling.

References

• https://developers.google.com/speed/webp/docs/riff_container
• https://developers.google.com/speed/webp/docs/api

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This skill combines wlframe, C, and struct-layout best practices for robust WebP format and libwebp integration.