Re: Thread safe?

FROM : Trygve Inda
DATE : Sat Mar 29 20:20:56 2008

> Yes.  See
>
> http://www.cocoabuilder.com/archive/message/cocoa/2007/11/15/193191
>
> ISTR having problems specifying a nonzero bytesPerRow and passing NULL
> for the bitmap data, so you might need to either manage the buffer
> yourself or pass zero for bytesPerRow to allow NSBitmapImageRep to pad
> it appropriately.


Many thanks.

>>
>>    [segImageRep dealloc];


> You should never call dealloc directly (well, unless you've overridden
> -retain/-release to handle your own refcounting).


Good catch!

>> How about:
>>
>> NSImage *    image = [[[NSImage alloc] initWithContentsOfFile:path]
>> autorelease];
>>
>>    [NSGraphicsContext saveGraphicsState];
>>    [NSGraphicsContext setCurrentContext:[NSGraphicsContext
>> graphicsContextWithBitmapImageRep:segImageRep]];
>>
>>    [image drawInRect:NSMakeRect(0, 0, [image size].width, [image
>> size].height) fromRect:NSMakeRect(0, 0, [image size].width, [image
>> size].height) operation:NSCompositeCopy fraction:1.0];
>>
>>    [NSGraphicsContext restoreGraphicsState];

>
> Drawing into an NSImage is explicitly documented to be thread safe in
> the article you linked to,


I guess I was more concerned with the initWithContentsOfFile:path

> and each thread has its own graphics
> context.  The post I linked to does indicate that you might want to
> use [image setCacheMode:NSImageCacheNever].  If your goal is just to
> get an NSBitmapImageRep from a file, it's probably easier just to use
> +imageRepWithContentsOfFile:.


This could work, but as I need to do pixel level manipulation, I really need
to know the exact format of the bitmap and this does not seem to let me
specify it.

Cheers,

Trygve