image-wasm v0.1.0

wasm-image-editor

An image processing library written entirely in WebAssembly and Rust (i.e. zero external or native dependencies).

JavaScript	WebAssembly

Try it

Try it: https://raphamorim.io/wasm-image-editor

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Grayscale

The Weighted Method:

Grayscale = 0.299R + 0.587G + 0.114B

Example (rust with casting between f32 and u8):

let grayscale = ((pixels[i] as f32 * 0.3) + (pixels[i+1] as f32 * 0.59) + (pixels[i+2] as f32 * 0.11)) as u8;

Average Method:

Grayscale = (R + G + B ) / 3

Theoretically, the formula is 100% correct. But when writing code, you may encounter uint8 overflow error. The sum of R, G, and B is greater than 255. To avoid the exception, R, G, and B should be calculated, respectively.

Grayscale = R / 3 + G / 3 + B / 3

Rust:

let pixels = unsafe { from_raw_parts_mut(data as *mut u8, len) };
let mut i = 0;
loop {
    if i >= len - 1 {
        break;
    }

    let grayscale = (pixels[i] / 3) + (pixels[i + 1] / 3) + (pixels[i + 2] / 3);
    pixels[i] = grayscale;
    pixels[i + 1] = grayscale;
    pixels[i + 2] = grayscale;
    i += 4;
}

Javascript:

const imageData = context.getImageData(0, 0, canvas.width, canvas.height);
const pixels  = imageData.data;
for (var i = 0, n = pixels.length; i < n; i += 4) {
    const grayscale = pixels[i] * .3 + pixels[i+1] * .59 + pixels[i+2] * .11;
    pixels[i] = grayscale;
    pixels[i+1] = grayscale;
    pixels[i+2] = grayscale;
}