how to change the color of an image in a 400x500 pixel rectangle in javascript in matlab

index.tsx
//Load the image onto the canvas
var img=document.getElementById('myImage');
var canvas=document.createElement('canvas');
var ctx=canvas.getContext('2d');
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img,0,0);

//Get the image data
var imageData=ctx.getImageData(0,0,400,500);

//Iterate over the pixels and change the color
for(var i=0;i<imageData.data.length;i+=4){
    if(imageData.data[i]==255 && imageData.data[i+1]==0 && imageData.data[i+2]==0){ //Red Color
        imageData.data[i]=0;
        imageData.data[i+1]=255;
        imageData.data[i+2]=0; //Green Color
    }
}

//Put the modified image data onto the canvas
ctx.putImageData(imageData,0,0);

//Replace the image with the modified canvas
img.src=canvas.toDataURL();
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