private void grayscale(ImageData image, ICanvasRenderingContext2D ctx)
{
ctx.drawImage(image, 0, 0);
uint imgWidth = image.width;
uint imgHeight = image.height;
var imageData = (ImageData) ctx.getImageData(0, 0, imgWidth, imgHeight);
for (ulong i = 0; i < imageData.height; i++)
{
for (ulong j = 0; j < imageData.width; j++)
{
ulong index = (i*4)*imageData.width + (j*4);
var red = (byte) imageData.data[index];
var green = (byte) imageData.data[index + 1];
var blue = (byte) imageData.data[index + 2];
var alpha = (byte) imageData.data[index + 3];
var average = (byte) ((red + green + blue)/3);
imageData.data[index] = average;
imageData.data[index + 1] = average;
imageData.data[index + 2] = average;
imageData.data[index + 3] = alpha;
}
}
ctx.putImageData(imageData, imageData.width + 5, 0, 0, 0, imageData.width, imageData.height);
}