[SDL] SDL_Image: IMG_isJPG() fails on pictures with IPTC information

[Jeremy Stanley]

Here's a proper unified diff from CVS for this patch. 


--- Jeremy Stanley <stanmuffin at yahoo.com> wrote:

> I found that SDL_Image fails to load JPEG files to
> which I have added a caption using Picasa (a free as
> in beer picture organization tool;
> http://www.picasa.com).  Picasa claims to store its
> captions in IPTC format.  Photoshop apparently uses
> this format too, but I don't have that program so I
> can't verify that.
> 
> The problem is that the IPTC information block is
> stored between the SOI (FF D8) and APP1 (FF E1)
> markers in the JPEG file, so that the "JFIF" or
> "Exif"
> constant is not stored at offset 6.  Instead, the
> two
> bytes at offset 2 store FF ED and the next two bytes
> store the size of the block as a big endian word
> (including the size field).  The APP1 (FF E1) marker
> will immediately follow.
> 
> A simple fix could be inserted just after the second
> SDL_RWread() in IMG_isJPG().  Instead of throwing
> these four bytes away, we can check for the IPTC
> header and skip over it.  The following code does
> the
> trick for me.
> 
> IMG_jpg.c
> 
> 49c49,52
> < 			SDL_RWread(src, magic, 4, 1);
> ---
> > 			SDL_RWread(src, magic, 4, 1);
> > 			if ( (magic[0] == 0xFF) && (magic[1] == 0xED) )
> {
> > 				SDL_RWseek(src, (((Uint16)magic[2] << 8) |
> magic[3]) + 2, SEEK_CUR);
> > 			}
> 
> 
> 
> 		
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