@pixi/utils/lib/media/getCanvasBoundingBox.js

Collection of utilities used by PixiJS

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

var BoundingBox = require('./BoundingBox.js');

function checkRow(data, width, y) {
  for (let x = 0, index = 4 * y * width; x < width; ++x, index += 4) {
    if (data[index + 3] !== 0)
      return false;
  }
  return true;
}
function checkColumn(data, width, x, top, bottom) {
  const stride = 4 * width;
  for (let y = top, index = top * stride + 4 * x; y <= bottom; ++y, index += stride) {
    if (data[index + 3] !== 0)
      return false;
  }
  return true;
}
function getCanvasBoundingBox(canvas) {
  const { width, height } = canvas;
  const context = canvas.getContext("2d", {
    willReadFrequently: true
  });
  if (context === null) {
    throw new TypeError("Failed to get canvas 2D context");
  }
  const imageData = context.getImageData(0, 0, width, height);
  const data = imageData.data;
  let left = 0;
  let top = 0;
  let right = width - 1;
  let bottom = height - 1;
  while (top < height && checkRow(data, width, top))
    ++top;
  if (top === height)
    return BoundingBox.BoundingBox.EMPTY;
  while (checkRow(data, width, bottom))
    --bottom;
  while (checkColumn(data, width, left, top, bottom))
    ++left;
  while (checkColumn(data, width, right, top, bottom))
    --right;
  ++right;
  ++bottom;
  return new BoundingBox.BoundingBox(left, top, right, bottom);
}

exports.getCanvasBoundingBox = getCanvasBoundingBox;
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