How to view raw binary data as an image with given width and height?

To see the "raw binary data", I would use the hex dump command hd or hexdump

$ hd -C a.txt
00000000  61 0a 61 61 0a 61 61 61  0a 61 61 61 61 0a 61 61  |a.aa.aaa.aaaa.aa|
00000010  61 61 61 0a 62 62 62 0a  62 62 62 62 0a 62 62 62  |aaa.bbb.bbbb.bbb|
00000020  62 62 0a 3c 62 65 67 69  6e 3e 0a 61 61 61 61 61  |bb.<begin>.aaaaa|
00000030  61 0a 61 61 61 61 61 61  61 0a 61 61 61 61 61 61  |a.aaaaaaa.aaaaaa|
00000040  61 61 0a                                          |aa.|
00000043

I don't know of any image format that consists of unstructured bytes - is the data 8-bit RGB values? If the file contains 30000 bytes is that RGB for 100x100 pixels or RGB for 50x200 pixels or RGB for 200x50 pixels or something else? Is there a palette? You have to know something about the organisation of the data!

To view it as an image I would use the NetPBM utilities or maybe ImageMagick to convert it to a form understood by an image viewer

If the above can't do the job I'd investigate writing a small Perl script

Okay, gnuplot can do it.

http://gnuplot.sourceforge.net/demo_4.4/image.html

convert from ImageMagick can do it.

E.g., an 8-bit 2x3 grayscale:

printf '\x00\xFF\x88\xFF\x00\xFF' > f

Then:

convert -depth 8 -size 3x2+0 gray:f out.png

Command explanation:

• -depth 8: each color has 8 bits
• -size 2x3+0: 2x3 image. +0 means starting at offset 0 in the file. If there are metadata headers, you can skip them with the offset.
• gray:f: the input file is f, and the format is gray, as defined at http://www.imagemagick.org/script/formats.php This weird notation is used because ImageMagick usually determines the format from the extension, but here there is no extension.

The problem now is how to view the output. A direct eog:

eog out.png

is not very good because the image is too small, and if you zoom in a lot eog uses a display algorithm that mixes up pixels, which is better for most pictures, but not in our case. I found two possibilities:

• gimp out.png. Image editors must show every single pixel.
• convert out.png -scale 300x200 out2.png. -scale is needed instead of -resize, since -resize mixels pixels up much like eog by default.

Output:

RGB example:

printf '\xFF\x00\x00\x00\xFF\x00\x00\x00\xFF' > f
convert -depth 8 -size 3x1+0 rgb:f out.png

Tested on Ubuntu 16.04, ImageMagick 6.8.9.