How can I write an image mat array (class:double) of values ranging from -182000 to 137081 into gray/color image file using 'imwrite' function? Because using the below code misses so many pixels in the final image.

load CT;
colormap(jet);
figure, imagesc(sum_CT);
set(gca,'XTickLabel',[],'YTickLabel',[]);
imwrite(sum_CT,'CT.bmp', 'bmp');

Answer 1

[Walter Roberson]

Have a look at the imwrite() documentation:

If the input array is of class double, and the image is a grayscale or RGB color image, imwrite assumes the dynamic range is [0,1] and automatically scales the data by 255 before writing it to the file as 8-bit values.

Any negative double values you try to write will thus end up clipped at 0.

If you are trying to write the equivalent of the imagesc() then you need to do the scaling yourself before you imwrite() the result.

[VENKATESAN]

Thanks for your answer... yes it happens... only I can see the 0 and 255 values in the resulting images. But, how can we use the scaling range(imagesc) to write the image with negative values too.. Thank you