Lorenzo Thurman wrote:
Sanders Kaufman wrote:
>For each of the image specs (gif, tiff, jpg, etc) the first few bytes
identify what it is. If you can binary read the first few bytes with
PHP, then you can get that info... and usually a lot of other stuff
(dimensions, pallet, (c), etc.)
Thanks for the reply. Do you know what I should check for? I know image
types often start with a unique binary header, but I don't know where to
find that info.
Whole books have been written on it, so there's more
than I can say here - but I can tell you how to dig
up the info yourself.
Here's the GIF specification:
"http://www.w3.org/Graphics/GIF/spec-gif89a.txt"
As you can see from the spec's sections 12-17, the
first few bytes contain meta-info about the image -
including the fact that it's a GIF. (You can grab
any old GIF and read it into PHP to see how the spec
plays out in the actual file.)
Once you master retrieving meta data about a GIF,
you can do the same thing with the specs for other
image formats, too - including binaries like
executables, ZIP's, and java or .NET assemblies.