How rescale and save image in Matlab?

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Neda 2019-5-16

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https://ww2.mathworks.cn/matlabcentral/answers/462443-how-rescale-and-save-image-in-matlab

评论： Neda 2019-5-21

I am reading a 'mhd' file which it's giving me an info like below:

 Filename: 'patient0001_2CH_ED_gt.mhd'
                 Format: 'MHA'
         CompressedData: 'false'
             ObjectType: 'image'
     NumberOfDimensions: 3
             BinaryData: 'true'
              ByteOrder: 'false'
        TransformMatrix: [1 0 0 0 1 0 0 0 1]
       CenterOfRotation: [0 0 0]
  AnatomicalOrientation: 'RAI'
                 Offset: [0 0 0]
        PixelDimensions: [0.3080 0.1540 1.5400]
             Dimensions: [549 778 1]
ElementNumberOfChannels: '1'
               DataType: 'uchar'
               DataFile: 'patient0001_2CH_ED_gt.raw'
               BitDepth: 8
             HeaderSize: 384

Then by another function I will read the info, then produce the image. Then, I need to rescale image dimension with pixel dimension ( PixelDimensions: [0.3080 0.1540 1.5400]), and I used imagescin order to do this like below code, but it change the unique value of my image. Is there any way to rescale the image without imagesc? alos imagesc produce 3 channels which I don't want, and apparently all channels are same.

rows = 1:info.Dimensions(1);
cols = 1:info.Dimensions(2);
Im2 = imagesc(rows.*info.PixelDimensions(1),cols.*info.PixelDimensions(2),Im(:,:)');
saveas(gcf,'Output_filename.png')

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Jurgen vL 2019-5-21

You are fundamentally misunderstanding what imagesc does. You want spatial resizing, not graylevel rescaling. Consider using imresize3.

Neda 2019-5-21

在 MATLAB Online 中打开

since, I am using 2dimension images, I used imresize., but still same problem. I have done it same as below. Could you please point me to the right direction?

info = SureScan_mhd_read_header('filename.mhd');
Im = SureScan_mhd_read_volume(info);
%rescale image based on info.PixelDimension, image need to be transposed as well
rows = 1:info.Dimensions(1);
cols = 1:info.Dimensions(2);
rows.*info.PixelDimensions(1),cols.*info.PixelDimensions(2),Im(:,:)'
%I did imresize image
im_2 = imresize(ans,[256 256],'nearest');
imshow(im_2) 
% it's all black while if I get b = unique(ans(:,:)) is include 0
,1, 2, 3
%then , I did imagsc to see the image
imagesc(im_2,[0 3]);colormap(gray)
saveas(gcf,'test_4.png')
test_4 = imread('test_4.png')
%when I save it like  saveas(gcf,'test_4.png'), and read it back again ; 
% image size is not 256 *256, and it's 545   672  3 while when I open png file,
% the axis displays 256 * 256