A QOI decoder written in the WebAssembly Text Format (WAT). Current size of the library is 549 bytes.
An implemention of the QOI decoder. This implementation is dependent on that the host can handle Multi-Value Wasm. Included is a compiled WAT to WASM file that can be instantiated to decode images. Demo is deployed here. (Note the requirements for the browser noted below.)
The wasm module assumes that the QOI data, including the header, is stored at memory index 0 before decompression. To decompress the data call the d method, e.g.,
const header = wasm.instance.exports.d();
const [width, height, channels, colorspace, memoryOffset] = header;
Where the width will be greater than zero if the data is a valid QOI. The memoryOffsets names the index where the decompressed data starts in the now expanded memory area.
In the viewer folder is an example on how to use the module. To view the example you need a browser that supports the File API, works on Chrome at the moment, does not work on Safari. There are two .qoi files in the assets folder that can be used as test input. To run the example locally
node serve.mjs
and point your compatible browser to QOI Viewer
To compile the project, install the dependencies and run the compile script
npm i
npm run compile
The ouput is the decoder file called qoi.wasm.
Another option is to inline the decompressor and the image data into a WASM module. After the module is loaded the instance exports a method called d (for decompress) and the memory (m) where the result will be after decompression. See below for memory layout, main difference here is that the decompressed data is stored at location 0.
npm run kombine file.qoi
If all goes well a new file will be written in the same folder as the src QOI file.
To see a runtime example running locally
npm run serve
and go to kombiner
To try the compilation step
npm run kombine ./assets/pixil-frame-0.qoi
and the compiled files will be stored in the assets folder.
Some example results. (sizes in bytes)
File PNG QOI QOI-WASM QOI-WASM-BROTLI
pixil-frame-o 124 104 530 308
peerfeer_frame_rgba 1684359 1747735 1748180 1019378
dice 349827 519653 520096 318018
kodim10 593463 652383 652820 499621
kodim23 557596 675251 675688 512840
qoi_logo 16605 16488 16925 7968
testcard_rgba 14227 24167 24605 9133
testcard 18371 21857 22295 7360
wikipedia_008 1344960 1521134 1521571 1225351
First two images are included in this repository, the rest comes from the official QOI page.
The WebAssembly Binary Toolkit for compiling the WAT files to WASM.
Brotli for compressing the inlined decompression module.