ppm-format

name	ppm-format
description	Use this skill when implementing, integrating, or reviewing PPM read/write C code in wlframe, especially portable pixmap parsing and generation in image, buffer, or related modules. Best for P3/P6 header parsing, max-value validation, ASCII and binary pixel decoding, and wlframe-style ownership and cleanup review.

PPM Format Integration Skill (wlframe/C Style)

When to Apply

Use this skill when implementing, integrating, or reviewing PPM read/write C code in wlframe, especially in image/, buffer/, or related modules.

PPM Format Essentials

• PPM (Portable Pixmap) is a simple, uncompressed ASCII (P3) or binary (P6) image format.
• Header: magic number (P3 or P6), width, height, max color value, then pixel data.
• Pixel data: RGB triplets, row-major order.

Integration & API Design

• Parse header strictly; validate magic number, dimensions, max value.
• Support both ASCII and binary variants.
• Convert pixel data to wlframe's internal format as needed.
• API prefix: wlf_ppm_. 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_ppm_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_ppm_load(struct wlf_ppm_image *out, const char *path);
bool wlf_ppm_save(const struct wlf_ppm_image *img, const char *path);
void wlf_ppm_finish(struct wlf_ppm_image *img);

Best Practices

• Check all allocation, I/O, and header parsing for errors.
• 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://netpbm.sourceforge.net/doc/ppm.html

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