Image Decoder
A software module that reads compressed image files and decompresses them into raw pixel data (RGB/RGBA buffer) for display or further processing.
An image decoder parses compressed image data in a specific format and reconstructs uncompressed pixel arrays. Decoding involves header parsing, data decompression, color space conversion, and applying EXIF Orientation rotation.
Browsers include built-in decoders for JPEG, PNG, GIF, WebP, and AVIF, invoked automatically by <img> tags or createImageBitmap(). However, HEIC and certain RAW formats require WebAssembly-compiled decoders since browsers lack native support.
Decode speed depends on file size and pixel dimensions. A 4000×3000 JPEG expands to approximately 36 MB in memory (4 bytes/pixel × 12 million pixels). Client-side processing must account for this memory footprint. The image conversion tool combines multiple decoders to support a wide range of input formats.