export async function getScreenshotBlocks()

in src/reporters/json.ts [289:342]

• 35 lines of code
• 3 McCabe index (conditional complexity)

export async function getScreenshotBlocks(screenshot: Buffer) {
  const { width, height } = await sharp(screenshot).metadata();
  /**
   * Chop the screenshot image (1280*720) which is the default
   * viewport size in to 64 equal blocks for a given image
   * which can be acheived by keeping the division to 8
   *
   * Changing division to 16 would yield us 256 smaller blocks, but it is not
   * optimal for caching in the ES and proved out to be bad, so we stick to 8
   */
  const divisions = 8;
  const blockWidth = Math.floor(width / divisions);
  const blockHeight = Math.floor(height / divisions);
  const reference: ScreenshotReference = {
    width,
    height,
    blocks: [],
  };
  const blocks: Array<ScreenshotBlob> = [];

  for (let row = 0; row < divisions; row++) {
    const top = row * blockHeight;
    for (let col = 0; col < divisions; col++) {
      const left = col * blockWidth;
      // We create a new sharp instance for each block to avoid
      // running in to extraction/orientation issues
      const buf = await sharp(screenshot, { sequentialRead: true })
        .extract({ top, left, width: blockWidth, height: blockHeight })
        .jpeg()
        .toBuffer();

      const hash = createHash('sha1').update(buf).digest('hex');
      blocks.push({
        blob: buf.toString('base64'),
        id: hash,
      });
      /**
       * We dont write the width, height of individual blocks on the
       * reference as we use similar sized blocks for each extraction,
       * we would need to send the width and height here if we decide to
       * go with dynamic block extraction.
       */
      reference.blocks.push({
        hash,
        top,
        left,
        width: blockWidth,
        height: blockHeight,
      });
    }
  }

  return { blocks, reference, blob_mime: 'image/jpeg' };
}