evanw/thumbhash
Thumbhash
Thumbhash is an image encoding library that converts images into compact strings to be used as lightweight placeholders. This format provides a binary representation of an image that preserves color and aspect ratio, allowing for the generation and rendering of blurred previews during page loads.
The project serves as an alternative to Blurhash by providing a method to encode images into tiny strings while avoiding high-frequency computational overhead. It also functions as a color palette extractor, enabling the derivation of the dominant average RGB color from an encoded representation for use in solid-color backgrounds.
The library covers a range of image processing capabilities, including dominant color extraction, compact image encoding, and the rendering of placeholders to support adaptive loading interfaces. These processes utilize discrete cosine transforms and bilinear interpolation to reconstruct low-resolution visual approximations from stored frequency coefficients.
Features
- Low-Quality Image Placeholder Previews - Encodes images into a compact format to generate smooth, low-quality preview placeholders for loading states.
- Discrete Cosine Transforms - Utilizes discrete cosine transforms to compress image data into a small set of frequency coefficients.
- Dominant Color Extraction - Calculates representative colors from image data for use in themed backgrounds or UI elements.
- Frequency Coefficient Reconstruction - Reconstructs low-resolution images by decoding stored frequency coefficients back into RGB values.
- Lightweight Placeholder Standards - Provides a lightweight encoding standard for placeholders that avoids the high-frequency overhead of traditional DCT transforms.
- Image Encoding Libraries - Provides a toolkit for converting images into compact strings and decoding them back into visual placeholders.
- Compact String Encodings - Converts visual data into tiny strings for efficient storage and transmission of image previews.
- Average Color Derivation - Retrieves the dominant average color of an image by processing encoded representation coefficients.
- Low-Quality Image Placeholders - Decodes compact encoded strings back into visual images to serve as optimized loading placeholders.
- Symmetric Quantization - Applies symmetric quantization to reduce the precision of coefficients for a more compact binary format.
- Alpha Channel Support - Supports images with non-opaque backgrounds by including transparency data within the compact encoding.
- Aspect Ratio Preservation - Stores original image proportions within the encoded data to prevent stretching during placeholder rendering.
- Interpolated Sampling - Uses bilinear interpolation to smooth transitions between decoded color blocks for a blurred effect.
- Image Color Extractors - Derives the dominant RGB average color from encoded image representations for solid-color backgrounds.
- Adaptive Resource Loading - Improves perceived load performance by serving immediate visual approximations before the full image arrives.
Star history
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