/**
* Trim transparent borders from a canvas
*
* @memberof PIXI.utils
* @function trimCanvas
* @param {HTMLCanvasElement} canvas - the canvas to trim
* @returns {object} Trim data
*/
export function trimCanvas(canvas) {
// https://gist.github.com/remy/784508
let width = canvas.width;
let height = canvas.height;
const context = canvas.getContext('2d');
const imageData = context.getImageData(0, 0, width, height);
const pixels = imageData.data;
const len = pixels.length;
const bound = {
top: null,
left: null,
right: null,
bottom: null,
};
let data = null;
let i;
let x;
let y;
for (i = 0; i < len; i += 4) {
if (pixels[i + 3] !== 0) {
x = (i / 4) % width;
y = ~~((i / 4) / width);
if (bound.top === null) {
bound.top = y;
}
if (bound.left === null) {
bound.left = x;
}
else if (x < bound.left) {
bound.left = x;
}
if (bound.right === null) {
bound.right = x + 1;
}
else if (bound.right < x) {
bound.right = x + 1;
}
if (bound.bottom === null) {
bound.bottom = y;
}
else if (bound.bottom < y) {
bound.bottom = y;
}
}
}
if (bound.top !== null) {
width = bound.right - bound.left;
height = bound.bottom - bound.top + 1;
data = context.getImageData(bound.left, bound.top, width, height);
}
return {
height,
width,
data,
};
}