Question

Is there any way to convert the image so it appears as a gray scale. Changing rgb is not working as required.

Answer 1

As you probably know, screen color consists of 3 components: red, green and blue. Each component or color (for example, red) has a value from 0 to 255. The value 0 indicates there is no red color and the value 255 would be the brightest possible red color. To convert a color to grayscale you just need to calculate the average for all three components. This can be done using the simple formula below:

grayscalecolor = (red + green + blue) / 3;

Canvas Method

var canvas = document.createElement('canvas');

var canvasContext = canvas.getContext('2d');

var imgW = imgObj.width;

var imgH = imgObj.height;
canvas.width = imgW;
canvas.height = imgH;
canvasContext.drawImage(imgObj, 0, 0);

var imgPixels = canvasContext.getImageData(0, 0, imgW, imgH);

for(>var y = 0; y < imgPixels.height; y++){
     for(>var x = 0; x < imgPixels.width; x++){
          var i = (y * 4) * imgPixels.width + x * 4;
          var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
          imgPixels.data[i] = avg;
          imgPixels.data[i + 1] = avg;
          imgPixels.data[i + 2] = avg;
     }
}
canvasContext.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);

return canvas.toDataURL();

Microsoft Internet Explorer does not support the CANVAS tag, but Microsoft does provide image manipulation through filters. The filter to use for converting images to grayscale is the filter named DXImageTransform.Microsoft.BasicImage.

imgObj.style.filter = 'progid:DXImageTransform.Microsoft.BasicImage(grayScale=1)';