fennec-image-compression: Скилл для сжатия и анализа изображений

--- name: fennec-image-compression description: Use this skill when asked to compress, resize, or analyze images in Go using the Fennec library, or when modifying the Fennec codebase itself. --- # Fennec Image Compression Skill Fennec is a pure-Go image compression library that uses SSIM-guided optimization to find the smallest file size that preserves visual quality. ## Core Architecture & Rules * **Pure Go:** Fennec has zero external dependencies and does not use cgo. Do not introduce third-party packages. * **SSIM-Guided:** Fennec binary-searches for the lowest JPEG quality that meets a target SSIM, rather than using arbitrary quality numbers. * **Format Auto-Selection:** Fennec automatically selects between JPEG and PNG based on factors like alpha transparency, color count, and edge density. ## Usage Examples ### 1. Basic File Compression (Quality-based) When a user wants to compress an image with a quality preset (Lossless, Ultra, High, Balanced, Aggressive, Maximum): ```go import "github.com/shamspias/fennec" opts := fennec.DefaultOptions() opts.Quality = fennec.Balanced // Targets SSIM ≥ 0.94 result, err := fennec.CompressFile("input.jpg", "output.jpg", opts) ``` ### 2. Target File Size Compression When hitting a specific file size target in bytes, Fennec uses a multi-strategy engine (JPEG quality search, color quantization, scaling): ```go opts := fennec.DefaultOptions() opts.TargetSize = 100 * 1024 // 100 KB opts.Format = fennec.Auto result, err := fennec.CompressFile("input.png", "output.jpg", opts) ``` ### 3. Resizing and Compressing Fennec uses Lanczos-3 interpolation with pre-multiplied alpha to prevent dark fringing on transparent edges: ```go opts := fennec.DefaultOptions() opts.MaxWidth = 1920 opts.MaxHeight = 1080 result, err := fennec.CompressFile("huge.jpg", "web.jpg", opts) ``` ### 4. Image Analysis To analyze an image's characteristics without compressing it: ```go img, err := fennec.Open("photo.jpg") stats := fennec.Analyze(img) // Returns stats.RecommendedFormat, stats.Entropy, stats.UniqueColors, etc. ``` ## Contributor Guidelines If you are tasked with modifying the Fennec codebase: * **Test Fixtures:** Fennec's integration tests rely on real image files in `testdata/`. If tests fail with "testdata missing", you must run `make fixtures` first to generate the synthetic deterministic images. * **Performance:** When modifying files like `compress.go` or `targetsize.go`, run `make bench` to check for memory allocation and performance regressions. * **SSIM Checks:** The `SSIM()` and `SSIMFast()` functions require `*image.NRGBA` inputs. Always ensure images are converted using `toNRGBA()` before comparison.