Printable View
hello every one.
i have tried the code posted on this site for reading images from C
but it is restricted to only 16 bit .Bmp images only.
i want to generalise it for the gif/jpeg formats(famous in internet)
which are widely used.
can any one help with required guidelines & suggestion
thank u all
Reading gif/jpeg is a TINY bit different than reading a bmp.
heh, a bit of an understatement :pQuote:
Originally posted by orbitz
Reading gif/jpeg is a TINY bit different than reading a bmp.
.GIF (pronounced "JIFF") is a proprietary format owned by CompuServe. with that said, you can find old tutorials on how to read/write it. You want probably GIF 32a.
It is much different than JPG/JPEG formats. GIF is a "lossless" algorithm-- no original data is lost. JPG/JPEG (Joint Photographic Experts Group) on the other hand is a "lossy" format. It discards "least significance" data in the rasterization (quantum) process. That's why JPG/JPEG images can be adjusted in size/quality-- how much data is thrown away determines how big the file is.
I've written both algorithms, and JPG/JPEG is by far the more difficult-- in fact, it's amazing how fast JPG/JPEG algorithms work, given the amount of code in them.
GIF is not "owned" by CompuServe, it's "owned" by the Unisys Corporation. One of those bland, evil American companies that looks perfectly harmless on the outside but they wear shiny uniforms and manufacture larger and larger death rays, so that one day they can death ray the entire world!!! :eek:
Not as bad as Microsoft, mind. :p
Anyways, Unisys doesn't "own" the GIF format as such, but they do have a patent out on the LZW implementation required to compress/decompress the data inside the GIF format.
My advice would be to seek out the Portable Network Graphics (PNG) format. It's free to use and pretty nifty too (Supports alpha channels, 32-bit image data, etc.). 'Tis the fooooooooooooootchaaaaaaaaaa...
Personally, I prefer TIFF. TIFF is the easiest format to read and write I've ever seen. Blissfully easy.
Quzah.
TIFF's are good and all, but JPEGS are really the best overall, they provide a very good compression ratio (lossy though) and are much more widely supported.
Yeah. I know why he wanted to read .JPG/.GIF. For my own use, because it's so easy, I prefer TIFF. If you're picking one to learn on they're a good starter. Very simple format. Easy to create your own images.Quote:
Originally posted by master5001
TIFF's are good and all, but JPEGS are really the best overall, they provide a very good compression ratio (lossy though) and are much more widely supported.
Or you could just use Java, which natively supports both JPG and GIF... :D
Quzah.
There are libraries that come with support for jpegs and gifs. I think if you are just getting started TIFFs aren't a bad way to go. I started off with bmp's which have some characteristics that make then a little harder for a newbie (which I wasn't when I started w/ bmp's). Java has better support for interacting with c programs now days, if only this were actually useful.
Intel used to have a free JPEG lib, but they scrapped it for a more powerful one that does lot's more stuff. I've seen JPEG algos and they're frightening! Truly wiz-kid stuff.
hehehe JPEGs are quite an advanced image format. Writing a JPEG reader by hand (not recommended) calls for algorithms such as Discrete Cosine Transformations and Huffman Coding. It is all fun stuff that will give you a head-ache.
Sorry, my bad. The reason it is commonly mentioned in collusion with Compuserve, rather than Unisys (you are correct) is because the original announcement was made by CompuServe, not Unisys when Unisys tried to enforce its patent. Here's specific info if you want it--Quote:
GIF is not "owned" by CompuServe, it's "owned" by the Unisys Corporation
http://lpf.ai.mit.edu/Patents/Gif/Gif.html
This is a windows only, JPEG only solution using the Intel Jpeg Library. I'll try to post the manual in next post.
For portable alternatives:
http://sourceforge.net/projects/freeimage
http://www.ijg.org/files/
Have Fun!
This is the manual. Sorry about the poor format but the pdf version was 205KB.