MATLAB: Counting pixel of an image

compressionimage thresholding

i have used the thresholding for image ..

the command is

length(find(abs(cw)<=50));
im(length(abs(cw)<=50))=0 ;

(1)for examble 42447 coeffients made to be zero out of 65656. my doubt is whether that remaing (23089 ) pixel only present in that image or else 0 will be presented for the whole 65536 ..

(2)how to count or calculate the number of pixels present in that image ?

(3)i apply the wavelet transform.. after that i apply this can i use this threshold for compression ?

pleased to ask reply from all ..

Best Answer

Responding to your comment

(1) The number of pixels under 50 is given more simply by

numPixelsLessThan50 = sum(sum(cw<50));

No need for find() and abs().

(2) A pixel contains the value of your image array at a certain location. I don't know what you are calling coefficients. I don't have the wavelet toolbox so I can't answer any questions about that.

(3)I don't understand what #3 is saying or asking. Something about wavelets, setting to zero, and compression but it's not clear. Ask someone else to reword it.

Related Solutions

MATLAB: Calculating the number of pixels inside a freehand region.

Since you are already using imfreehand, you can use the method named createMask available in the imfreehand object to rasterize the marked region into a binary image. Then you can just use logical AND to combine the binary image with your original image and sum over all the pixels in the image to get the desired count. I think the code would look something as follows. Say your image is called I.

figure, imshow(I)
f = imfreehand; 
% Then draw the region using imfreehand tool
bw = createMask(f);
outI = bw.*I;
numPixelsInsideRegion = sum(outI(:))

MATLAB: Converting boundary to mask

b=bwboundaries(BW);   % BW being your binary image
mask=false(size(BW));
for i = 1:length(b)
    for j = 1:length(b{i})
        ind = b{i}(j,:);
        mask(ind(1),ind(2))=1;
    end
end
figure
imshow(mask)

Best Answer

Related Solutions

MATLAB: Calculating the number of pixels inside a freehand region.

MATLAB: Converting boundary to mask

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