image-js/lib/geometry/rotate.js

Image processing and manipulation in JavaScript

import { Image } from '../Image.js';
/**
 * Rotates an image in multiples of 90 degrees.
 * @param image - The image to rotate.
 * @param angle - The angle to rotate the image by. Positive values rotate clockwise, negative values rotate counter-clockwise.
 * @returns - The rotated image.
 */
export function rotate(image, angle) {
    const newWidth = angle % 180 === 0 ? image.width : image.height;
    const newHeight = angle % 180 === 0 ? image.height : image.width;
    const newImage = Image.createFrom(image, {
        width: newWidth,
        height: newHeight,
    });
    if (angle === 90 || angle === -270) {
        for (let column = 0; column < image.width; column++) {
            for (let row = 0; row < image.height; row++) {
                for (let channel = 0; channel < image.channels; channel++) {
                    newImage.setValue(newImage.width - row - 1, column, channel, image.getValue(column, row, channel));
                }
            }
        }
    }
    else if (angle === 180 || angle === -180) {
        for (let column = 0; column < image.width; column++) {
            for (let row = 0; row < image.height; row++) {
                for (let channel = 0; channel < image.channels; channel++) {
                    newImage.setValue(newImage.width - column - 1, newImage.height - row - 1, channel, image.getValue(column, row, channel));
                }
            }
        }
    }
    else if (angle === 270 || angle === -90) {
        for (let column = 0; column < image.width; column++) {
            for (let row = 0; row < image.height; row++) {
                for (let channel = 0; channel < image.channels; channel++) {
                    newImage.setValue(row, newImage.height - column - 1, channel, image.getValue(column, row, channel));
                }
            }
        }
    }
    else {
        throw new RangeError(`invalid angle: ${angle}`);
    }
    return newImage;
}
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