how to divide an image of 400x500pixels into 100 blocks each of size 40x50 pixels

how to divide an image of 400x500 pixels into 100 blocks each of size 40x50 pixels.and check each blocks for threshold value and turn whole block into white depending upon threshold value

Answer 1

[Image Analyst]

Two different ways are shown in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_split_an_image_into_non-overlapping_blocks.3F. Inside the loop, you can call graythresh() or some other threshold picking algorithm, and im2bw().

[ramya sharma]

Thank u so much but what should i do if i hv to combine it again after performing some operations like turning some blocks to white

[Image Analyst]

You have to keep track of what the indexes are for the block you're in, and then just write directly to that block in image. For example if you know you're processing rows 30-40 and columns 400-420, you'd do this to turn it white

yourImage(30-40, 400-420) = 255;

[ramya sharma]

actually my question is how to recombine the image after dividing it into blocks

[Image Analyst]

If you can, it might be best to just process it in place without chopping up into separate variables or cells. But if you must have different images, then you can stitch them together like this:

tallImage = [topImage; bottomImage];
wideImage = [leftImage, rightImage];

You'll need to change the images as you move along from blobk to block.