Re: Reading Adobe Photoshop header, Obj-C
Re: Reading Adobe Photoshop header, Obj-C
- Subject: Re: Reading Adobe Photoshop header, Obj-C
- From: Thomas Engelmeier <email@hidden>
- Date: Tue, 28 Jun 2011 21:47:44 +0200
On 28.06.2011, at 15:23, Kevin Muldoon wrote:
> Was writing a program to create thumbnails using SIPS, GhostScript, ImageMagick. During testing I found I needed to read the header file of Adobe Photoshop native documents directly because Duotone image color mode simply wasn't returning the proper color mode (in a variety of programs).
>
> So I threw together this bit of code which works great for the first tag, but....
>
> // References
> //http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm#50577409_pgfId-1055726
> //http://www.adobe.com/content/dam/Adobe/en/devnet/photoshop/psir/ps_image_resources.pdf
>
> NSFileHandle *fileHandler = [NSFileHandle fileHandleForReadingAtPath:@"/Users/kevin/Desktop/balloon.psd"];
>
> NSData *psdFileHeader = [NSData dataWithData:[fileHandler readDataOfLength:26]]; // read entire PSD header
>
> NSData *signature = [psdFileHeader subdataWithRange: NSMakeRange(0,4)];
> NSData *version = [psdFileHeader subdataWithRange: NSMakeRange(4,2)];
> NSData *reserved = [psdFileHeader subdataWithRange: NSMakeRange(6,6)];
You're doing the worst case for performancewise.
The usual way would be to define a struct
#pragma pack (push, 2)
typedef struct {
uint32_t psdMagic;
uint16_t version;
uint16_t reserved1;
uint32_t reserved2;
} PSDHeader;
and use it with code like:
NSData * psdHdrData = [NSData dataWithData:[fileHandler readDataOfLength:sizeof( PSDHeader )]]; // read entire PSD header
PSDHeader *header = (psdHeader *) [psdHdrData bytes];
psdMagic = CFEndianBToN( header->psdMagic );
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