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javascripthtml5-canvas

Crop images according to the white spaces in javascript

I'm working on a Javascript project and im a bit stuck. I want to make a function that takes an image as parameter an returns the same image but with cropped blank spaces. Here's an example:

Before

before

After

after

I tried this function that i found on stack :

function removeImageBlanks(imageObject) {
    imgWidth = imageObject.width;
    imgHeight = imageObject.height;
    var canvas = document.createElement('canvas');
    canvas.setAttribute("width", imgWidth);
    canvas.setAttribute("height", imgHeight);
    var context = canvas.getContext('2d');
    context.drawImage(imageObject, 0, 0);

    var imageData = context.getImageData(0, 0, imgWidth, imgHeight),
        data = imageData.data,
        getRBG = function(x, y) {
            var offset = imgWidth * y + x;
            return {
                red:     data[offset * 4],
                green:   data[offset * 4 + 1],
                blue:    data[offset * 4 + 2],
                opacity: data[offset * 4 + 3]
            };
        },
        isWhite = function (rgb) {
            // many images contain noise, as the white is not a pure #fff white
            return rgb.red > 200 && rgb.green > 200 && rgb.blue > 200;
        },
                scanY = function (fromTop) {
        var offset = fromTop ? 1 : -1;

        // loop through each row
        for(var y = fromTop ? 0 : imgHeight - 1; fromTop ? (y < imgHeight) : (y > -1); y += offset) {

            // loop through each column
            for(var x = 0; x < imgWidth; x++) {
                var rgb = getRBG(x, y);
                if (!isWhite(rgb)) {
                    if (fromTop) {
                        return y;
                    } else {
                        return Math.min(y + 1, imgHeight);
                    }
                }
            }
        }
        return null; // all image is white
    },
    scanX = function (fromLeft) {
        var offset = fromLeft? 1 : -1;

        // loop through each column
        for(var x = fromLeft ? 0 : imgWidth - 1; fromLeft ? (x < imgWidth) : (x > -1); x += offset) {

            // loop through each row
            for(var y = 0; y < imgHeight; y++) {
                var rgb = getRBG(x, y);
                if (!isWhite(rgb)) {
                    if (fromLeft) {
                        return x;
                    } else {
                        return Math.min(x + 1, imgWidth);
                    }
                }      
            }
        }
        return null; // all image is white
    };

    var cropTop = scanY(true),
        cropBottom = scanY(false),
        cropLeft = scanX(true),
        cropRight = scanX(false),
        cropWidth = cropRight - cropLeft,
        cropHeight = cropBottom - cropTop;

    canvas.setAttribute("width", cropWidth);
    canvas.setAttribute("height", cropHeight);
    // finally crop the guy
    canvas.getContext("2d").drawImage(imageObject,
        cropLeft, cropTop, cropWidth, cropHeight,
        0, 0, cropWidth, cropHeight);

    return canvas.toDataURL();
}

But it i am still stuck with the error :

index.js:63 Uncaught DOMException: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The canvas has been tainted by cross-origin data.
at removeImageBlanks (http://127.0.0.1:5500/index.js:63:29)
at <anonymous>:1:1

I already tried to add img.crossOrigin = 'Anonymous'; but it still does not work.

Solution

  • Use same domain image or use image base64 data URI instead of url.