tom-weatherhead/thaw-image-processing.ts

// thaw-image-processing.ts/src/map-colours.ts

import { IThAWImage, ThAWImageBufferType } from './image';

export type ColourMapperType = (
    buffer: ThAWImageBufferType,
    offset: number
) => void;

export function seeingRedRGBA( // ColourMapperType
    buffer: ThAWImageBufferType,
    offset: number
): void {
    buffer[offset + 2] = 0;
    buffer[offset + 1] = 0;
}

export function mapColoursInImageFromBuffer(
    srcImage: IThAWImage,
    fnMapColours: ColourMapperType
): IThAWImage {
    const bytesPerPixel = 4; // Assume that the pixel format is RGBA.

    const width = srcImage.width;
    const height = srcImage.height;
    const bytesPerLine = width * bytesPerPixel;
    const buffer = srcImage.data;
    let rowOffset = 0;

    for (let row = 0; row < height; row++) {
        let pixelOffset = rowOffset;

        for (let col = 0; col < width; col++) {
            fnMapColours(buffer, pixelOffset);
            pixelOffset += bytesPerPixel;
        }

        rowOffset += bytesPerLine;
    }

    return srcImage;
}