How can we pass gpuArray in Cdata of imshow?

Question

JAI PRAKASH 2018-7-11

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https://ww2.mathworks.cn/matlabcentral/answers/409899-how-can-we-pass-gpuarray-in-cdata-of-imshow

评论： Tomycj 2022-10-29

finalImage = imshow(gpuArray(imread(imName)));  % this is OK
BUT
set(finalImage,'CData',gpuArray(imread(imName))) ; % Is showing error
Error using matlab.graphics.primitive.Image/set
Error setting property 'CData' of class 'Image':
Value must be either:
Truecolor - a 4xN array of type numeric or logical type
Colormapped - an MxN vector of numeric or logical type

I am using this set CData in a while loop to save time.

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Answer 1

Rik 2018-7-11

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Because image is not holding your hand (and imshow is), you need to do the work yourself. In this case that means you need to get the data from the gpuArray back out to a normal array with the gather function. I'm not sure if this will get you any speed increase compared to skipping the call to gpuArray in the first place.

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Tomycj 2022-10-29

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So while creating and image object, the input array is automatically gathered, but not when you want to manually change its value? Is that what is happening here below?

M1 = gpuArray([1 2 3])
im=image('CData', M1,'CDataMapping','direct');  % This works
im.CData = M1                                   % This doesn't
im.Cdata = gather(M1)                           % This works, but is VERY slow