reading bands in .tiff file.

I have decomposed sentinel-1 SLC image. The result gave the Entropy image whose pixel value ranges from 0 to 1(image has only one band). the image is converted to .tiff file. and imported to Matlab. the image array is showing values in the grey scale i.e. 0-255, But the band having entropy value is also showing same values in gray scale. How to get entropy values from the image which is in the range(0-1).

the code i have followed as follows

[entropy, R] = readgeoraster("subset_2_of_S1A_IW_SLC__1SDV_20211028T004043_20211028T004110_040312_04C6EF_A357_Spk_Decomp_TC_Cnv.tif");
info = geotiffinfo("subset_2_of_S1A_IW_SLC__1SDV_20211028T004043_20211028T004110_040312_04C6EF_A357_Spk_Decomp_TC_Cnv.tif");
Entropy_val = entropy(:,:,1);

Answer 1

[yanqi liu]

yes，sir，may be use

entropy = mat2gray(entropy);

[Keerthana N]

Thank you, I have a doubt here. For example if we pre-process image in SNAP software, the output image will have bands with some values in .img and .hdr format. When we convert the image to .tiff file, the values get converted to gray scale(0 to 255). When i compared the values considereing particular pixel. i could observe difference in values.

At pixel X = 1757, Y = 1971

the entropy values shown in orginal image is 0.63127

the entropy values when the .img image converted to .tiff is 88

using, entropy = mat2gray(entropy); the value shown is 0.3451(88/255)

Is there any way to get original value?

[Walter Roberson]

Do not use mat2gray() when you need absolute values. mat2gray() finds the minimum data value and maximum data value and scales between those two values.

If you need absolute values, then you should be using im2double() or im2uint8() or im2uint16() or im2int16() depending on the context.

[Keerthana N]

@Walter Roberson im2double() gives same values like mat2gray(), other three gives are not suitable. is there any other way?

[Walter Roberson]

We will need to have a look at the way that you convert the hdr img files to tiff

[yanqi liu]

yes，sir，as up friend suggest，use im2doule、double(matrix)/255 can get double value