Cropping image to 8 bit

hai friends,,i want to ask about how to cropping the image to 256 x 256 piksel (8 bit) using matlab??? Thankyou before

Answer 1

[Walter Roberson]

im2uint8()

[dinda ayusma]

thankyou Walter..

but where this coding i put?

if my coding like this?

im=imread('b1.jpg')
imshow(im)
imcrp=imcrop(im,[50,50,80,80])
imshow(imcrp)

which i must to change?

[Walter Roberson]

You currently imcrop [50, 50, 80, 80] which crops an 80 x 80 rectangle (or 81 x 81 sometimes). If you want 256 x 256 you would change the 80,80 to 256, 256 and possibly adjust the 50, 50.

But an image that is 256 pixels by 256 has nothing to do with 8 bits per pixel. You are reading from a .jpg file, and those are almost always 8 bits per pixel color images that will read in as uint8 .

[dinda ayusma]

So im make 8 bit piksels use like photosoph tools?

[Walter Roberson]

im = imread('wagon.jpg');

subplot(2,2,1)
imshow(im)
title('original')

imcrp = imcrop(im,[50,50,256,256]);
subplot(2,2,2)
imshow(imcrp)
title('cropped')

im8 = im2uint8(imcrp);
subplot(2,2,3)
imshow(im8)
title('8 bit')

if isa(imcrp, 'uint8')
    fprintf('Input image was ALREADY uint8\n');
else
    fprintf('Input image was class %s, now converted to uint8\n', class(imcrp));
end

Input image was ALREADY uint8

d8 = double(im8);
img8p = uint8(cat(3, floor(d8(:,:,1)/64)*64, floor(d8(:,:,2)/32)*32, floor(d8(:,:,3)/64)*64));
subplot(2,2,4)
imshow(img8p)
title('pixelized to 8 bits')

[dinda ayusma]

Thankyou Walter Roberson.

[dinda ayusma]

[dinda ayusma]

how to the object rice is in the middel??

[Walter Roberson]

Use regionprops to find the bounding box. imcrop() to the bounding box.

If necessary, pad the array with zeros https://www.mathworks.com/help/images/ref/padarray.html

[dinda ayusma]

im sorry., where should I add it?

[Walter Roberson]

im = imread('rice.png');
if ndims(im) < 3; im = repmat(im, 1, 1, 3); end

subplot(2,2,1)
imshow(im)
title('original')

im2 = imbinarize(rgb2gray(im));
im2 = bwareafilt(im2, 10);
props = regionprops(im2, 'boundingbox');
oneBB = props(1).BoundingBox;
imcrp = imcrop(im, oneBB);
subplot(2,2,2)
imshow(imcrp)
title('cropped')
im8 = im2uint8(imcrp);
subplot(2,2,3)
imshow(im8)
title('8 bit')
if isa(imcrp, 'uint8')
    fprintf('Input image was ALREADY uint8\n');
else
    fprintf('Input image was class %s, now converted to uint8\n', class(imcrp));
end

Input image was ALREADY uint8

d8 = double(im8);
img8p = uint8(cat(3, floor(d8(:,:,1)/64)*64, floor(d8(:,:,2)/32)*32, floor(d8(:,:,3)/64)*64));
subplot(2,2,4)
imshow(img8p)
title('pixelized to 8 bits')

[dinda ayusma]

why not detected variabel imbinarize?