MATLAB: Free hand cropping an image

croppingfree handfreeformimage processingImage Processing Toolbox

Hello all,

I saw this post recently on this forum by Sean de Wolski on 19 Jun 2013. This is to free hand crop an image and blackout the rest. However, I'm using a jpg and it's causing the rest of my image to have a blueish tint. Do you know how to fix this? Thanks in advance!!

I = imread('cameraman.tif');

imshow(I);

h = imfreehand; %draw something

M = ~h.createMask();

I(M) = 0;

imshow(I);

Best Answer

Don't use jpg images. I never do. They are not suitable for doing image analysis. Use PNG format because it's lossless compression.

I used your code and did not get a bluish tint.

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MATLAB: Assign black pixels to binary image

If "mask" is your binary image, and you want the white parts to be black (and the original pixels in the black areas of your binary image left unaltered) in your original grayscale or rgb image , called "yourImage", do this:

% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedImage = bsxfun(@times, yourImage, cast(~mask, 'like', yourImage));

MATLAB: Can I calculate the amount of black and white pixels inside a freehand region

The mask just tells you which pixels are in the region. To count the black pixels within the mask, you need to look at both in the region and the value in the original image. Something like this:

nBlack1 = sum(sum(Image1 & ~origImage))

Best Answer

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MATLAB: Assign black pixels to binary image

MATLAB: Can I calculate the amount of black and white pixels inside a freehand region

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