image-js/lib/operations/convertBitDepth.js

Image processing and manipulation in JavaScript

import { getOutputImage } from '../utils/getOutputImage.js';
/**
 * Convert the bit depth of an image.
 * @param image - Image to convert.
 * @param newBitDepth - Bit depth to convert to.
 * @param options - Convert bit depth options.
 * @returns Converted image.
 */
export function convertBitDepth(image, newBitDepth, options = {}) {
    if (image.bitDepth === newBitDepth) {
        return getOutputImage(image, options, { clone: true });
    }
    if (newBitDepth !== 8 && newBitDepth !== 16) {
        throw new RangeError(`This image bit depth is not supported: ${newBitDepth}`);
    }
    // Get the output image first - this handles the out option
    const newImage = getOutputImage(image, options, {
        clone: false,
        newParameters: {
            bitDepth: newBitDepth,
            colorModel: image.colorModel,
        },
    });
    return newBitDepth === 8
        ? convertToUint8(image, newImage)
        : convertToUint16(image, newImage);
}
/**
 * Convert bit depth to 16 bits.
 * @param image - Image to convert.
 * @param targetImage - Target image to write to.
 * @returns Converted image.
 */
function convertToUint16(image, targetImage) {
    for (let i = 0; i < image.size; i++) {
        for (let j = 0; j < targetImage.channels; j++) {
            targetImage.setValueByIndex(i, j, image.getValueByIndex(i, j) << 8);
        }
    }
    return targetImage;
}
/**
 * Convert bit depth to 8 bits.
 * @param image - Image to convert.
 * @param targetImage - Target image to write to.
 * @returns Converted image.
 */
function convertToUint8(image, targetImage) {
    for (let i = 0; i < image.size; i++) {
        for (let j = 0; j < targetImage.channels; j++) {
            targetImage.setValueByIndex(i, j, image.getValueByIndex(i, j) >> 8);
        }
    }
    return targetImage;
}
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