check image bit-depth without an image library

[dlite922]

Hey guys,

I have limited access to a server and would be a pain to install and configure an image library such as GD or Imagick with PHP.

Is there any other progmatically some-what reliable way to check the bit-depth of a png or jpg image? (e.g. 16-bit, 32-bit, 64-bit)

This of course, means opening up the file and taking a peek inside, but the files look different.

There's no such thing as a bad idea, just untried ones, so fire away!





Dan

EDIT: Can somebody post what JPEG Analyzer does? (limited google access), thanks.

[Amzul]

umm maybe you can try to fopen the file then read line by line and search for png structure

fopen with binary read flag maybe

[dlite922]

@Amzul
Ya, I tried this, my images weren't consistent and I didn't see a pattern.

some have JFIF header info, some don't.

As a temporary solution I used imagick CLI: "identify -verbose"
If there is an alpha channel, I return 32, else if Pallete type, its 8 bit, else if TrueColor return 24 bit. else -1.

I tested it with the three bit-depth and seems to work enough.

I also tried getimagesize() which gives you a "bits" value, but it was always 8 for all of the above image depth and returned 1 for an image who was just all FF0000.

my files are 100% PNG.





Dan

[hsriat]

Did you try to do some mathematical calculations with the number of bits each 'row of pixels' contain and the length after which 'end of row bit pattern' repeats?