resize and crop image buffer without buffer in javascript

To resize and crop an image buffer in JavaScript, we can use the canvas element of HTML5. Here is an example code snippet:

index.tsx
// image buffer: assume it's a Uint8ClampedArray or Uint8Array with RGBA values in linear layout
const originalBuffer = new Uint8ClampedArray(width * height * 4);

// a new canvas element
const canvas = document.createElement('canvas');

// set canvas dimensions
canvas.width = newWidth;
canvas.height = newHeight;

// get canvas context (2D)
const ctx = canvas.getContext('2d');

// create original ImageData object
const originalImageData = new ImageData(originalBuffer, width, height);

// draw original ImageData object onto cropped area in canvas
ctx.putImageData(originalImageData, -cropX, -cropY);

// retrieve ImageData object from the canvas (already cropped)
const croppedImageData = ctx.getImageData(0, 0, newWidth, newHeight);

// create a new image buffer to store the cropped image
const croppedBuffer = croppedImageData.data;
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In this example code snippet, originalBuffer is the original image buffer with RGBA values, width and height are the dimensions of the original image, newWidth and newHeight are the new dimensions desired after cropping and resizing, cropX and cropY are the dimensions to be cropped from the original image. The code first creates a new canvas element and sets its dimensions, then retrieves the 2D context of the canvas. The original ImageData object is created with the original image buffer, width, and height. Then, by using putImageData() method, the original image data is drawn onto cropped area. Using getImageData() method, the cropped ImageData object is obtained from the canvas. Finally, the RGBA values of the cropped ImageData object are stored in a new buffer, croppedBuffer.