JS Client-Side Exif Orientation: Rotate and Mirror JPEG Images

Question

Digital camera photos are often saved as JPEG with an EXIF \"orientation\" tag. To display correctly, images need to be rotated/mirrored depending on which orientation is se

Answer 1

WunderBart's answer was the best for me. Note that you can speed it up a lot if your images are often the right way around, simply by testing the orientation first and bypassing the rest of the code if no rotation is required.

Putting all of the info from wunderbart together, something like this;

var handleTakePhoto = function () {
    let fileInput: HTMLInputElement = document.getElementById('photoInput');
    fileInput.addEventListener('change', (e: any) => handleInputUpdated(fileInput, e.target.files));
    fileInput.click();
}

var handleInputUpdated = function (fileInput: HTMLInputElement, fileList) {
    let file = null;

    if (fileList.length > 0 && fileList[0].type.match(/^image\//)) {
        isLoading(true);
        file = fileList[0];
        getOrientation(file, function (orientation) {
            if (orientation == 1) {
                imageBinary(URL.createObjectURL(file));
                isLoading(false);
            }
            else 
            {
                resetOrientation(URL.createObjectURL(file), orientation, function (resetBase64Image) {
                    imageBinary(resetBase64Image);
                    isLoading(false);
                });
            }
        });
    }

    fileInput.removeEventListener('change');
}


// from http://stackoverflow.com/a/32490603
export function getOrientation(file, callback) {
    var reader = new FileReader();

    reader.onload = function (event: any) {
        var view = new DataView(event.target.result);

        if (view.getUint16(0, false) != 0xFFD8) return callback(-2);

        var length = view.byteLength,
            offset = 2;

        while (offset < length) {
            var marker = view.getUint16(offset, false);
            offset += 2;

            if (marker == 0xFFE1) {
                if (view.getUint32(offset += 2, false) != 0x45786966) {
                    return callback(-1);
                }
                var little = view.getUint16(offset += 6, false) == 0x4949;
                offset += view.getUint32(offset + 4, little);
                var tags = view.getUint16(offset, little);
                offset += 2;

                for (var i = 0; i < tags; i++)
                    if (view.getUint16(offset + (i * 12), little) == 0x0112)
                        return callback(view.getUint16(offset + (i * 12) + 8, little));
            }
            else if ((marker & 0xFF00) != 0xFF00) break;
            else offset += view.getUint16(offset, false);
        }
        return callback(-1);
    };

    reader.readAsArrayBuffer(file.slice(0, 64 * 1024));
};

export function resetOrientation(srcBase64, srcOrientation, callback) {
    var img = new Image();

    img.onload = function () {
        var width = img.width,
            height = img.height,
            canvas = document.createElement('canvas'),
            ctx = canvas.getContext("2d");

        // set proper canvas dimensions before transform & export
        if (4 < srcOrientation && srcOrientation < 9) {
            canvas.width = height;
            canvas.height = width;
        } else {
            canvas.width = width;
            canvas.height = height;
        }

        // transform context before drawing image
        switch (srcOrientation) {
            case 2: ctx.transform(-1, 0, 0, 1, width, 0); break;
            case 3: ctx.transform(-1, 0, 0, -1, width, height); break;
            case 4: ctx.transform(1, 0, 0, -1, 0, height); break;
            case 5: ctx.transform(0, 1, 1, 0, 0, 0); break;
            case 6: ctx.transform(0, 1, -1, 0, height, 0); break;
            case 7: ctx.transform(0, -1, -1, 0, height, width); break;
            case 8: ctx.transform(0, -1, 1, 0, 0, width); break;
            default: break;
        }

        // draw image
        ctx.drawImage(img, 0, 0);

        // export base64
        callback(canvas.toDataURL());
    };

    img.src = srcBase64;
}