Load and display bitmap file using Fread

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Bmp files have header usually of 54 bytes.How can i get rid of it to display my bmp by using fread.i tried by following code.but the image i get has disorted color.How can i get rid of header and reshape in a way that color dont get disturbed
fid=fopen("m.bmp",'rb')
f=fread(fid,'uint8')
a=reshape(f,512,512,3)

Accepted Answer

Walter Roberson
Walter Roberson on 14 Nov 2021
Edited: Walter Roberson on 14 Nov 2021
Pixel Data
an array of bytes that defines the bitmap bits. These are the actual image data, represented by consecutive rows, or "scan lines," of the bitmap. Each scan line consists of consecutive bytes representing the pixels in the scan line, in left-to-right order. The system maps pixels beginning with the bottom scan line of the rectangular region and ending with the top scan line.
[...]
RGB values are stored backwards i.e. BGR.
(I interpret this as meaning that you have the B, G, R for the left-bottom pixel, then the B, G, R for the one to the right of that, and so on, then the B, G, R for the second-from the bottom left pixel, and so on. Eventually the end of the file would be B, G, R for the top right corner.)

More Answers (1)

Rik
Rik on 13 Nov 2021
You should reshape the data, not the fid. To remove the first 54 bytes you can use fseek, or just skip it from your array:
fid=fopen("m.bmp",'rb');
f=fread(fid,'uint8');
fclose(fid);
a=reshape(f(55:end),512,512,3);
  2 Comments
Rik
Rik on 14 Nov 2021
Then the arrangement might be different from what reshape assumes. Have you tried different orientations?

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