spatial transformation of image

Hi guys, I am beginner to MATLAB.

How to convert one normal image(either gray or rgb) to 1 bit, 2 bit, 3 bit, 4 bit and 8 bit through spatial transformation?

Thanks.

Answer 1

[Image Analyst]

You can't do that. You can transform the image spatially with function like imwarp(), imtranslate(), etc. but they won't change the bit depth.

See attached bit plane demo.

[Allen Ray]

Hi friend, is there any way to sample the original image to 1,2,3,4,8 bits? Perhaps through spatial transformation?

[Image Analyst]

Like I already said, no. No matter how you spatially transform the image, if all you're doing is moving pixels to new locations or whatever, then it won't change the bit depths. You need an intensity transform, such as dividing the image by 64 or 128 or whatever, to change the bit depth.

[Allen Ray]

Can you kindly show me the way? Sorry, I am really new to this :(

[Image Analyst]

Try dividing or thresholding:

image1bit = yourImage > thresholdValue;
image2bit = yourImage / 2^6;
image3bit = yourImage / 2^5;
image4bit = yourImage / 2^4;
image5bit = yourImage / 2^3;
image6bit = yourImage / 2^2;
image7bit = yourImage / 2^1;

[Allen Ray]

One question again. What happen to this picture? Is the bits have changed or the pixel changed?How can get an image to be like that?

[Allen Ray]

[Allen Ray]

After I tried to follow your code, why the picture became darker and darker(from image7bit to image2bit)?

[Image Analyst]

In your picture, you're changing the spatial resolution of the image, not the intensity resolution which is the bit depth.

Of course if the intensities are only 2 bits, the intensities can be 0, 1, 2, or 3, so of course that's going to be darker than an image with 8 bits where the values can go as high as 255.

To reduce the spatial resolution of the image, you can use imresize, with the 'nearest' option, both to shrink it and to magnify it.

grayImage = imread('cameraman.tif');
subplot(3,1,1);
imshow(grayImage);
axis on;

smallImage = imresize(grayImage, 1/16, 'nearest');
subplot(3,1,2);
imshow(smallImage);
axis on;

bigImage = imresize(smallImage, 16, 'nearest');
subplot(3,1,3);
imshow(bigImage);
axis on;