Am 30.03.2008 um 17:01 schrieb Adam R. Maxwell:
On Mar 30, 2008, at 6:10 AM, Thomas Engelmeier wrote:
On 29.03.2008, at 18:54, Adam R. Maxwell wrote:
Drawing into an NSImage is explicitly documented to be thread safe
in the article you linked to, 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:.
While it is documented to be thread save you might get crashes
later when an NSBitmapImageRep created by drawing into from an
secondary thread gets drawn itself. The crash occurs when the image
tries to access an NULL (offscreen) window context (it probably was
originally drawn into).
Tried to debug that on 10.5.2 (and simply worked around)...
That's interesting. Was it an NSBitmapImageRep or NSImage/
NSCachedImageRep? I didn't think a bitmap context would be
associated with a window context like that. Either way it doesn't
sound good, though.
Well, actually an NSTIFFImageRep. The crashing code (other thread,
much later, ...):
NSData *data = [anImage
TIFFRepresentationUsingCompression:NSTIFFCompressionLZW factor:1.0];
/* gives an crash in
FREED(id): message _tryLockViewHierarchyForModification sent to freed
object=0xeee5b40
#1 0x90063ef0 in __objc_error ()
#2 0x900628f7 in _freedHandler ()
#3 0x92f807c2 in _NXAllocateImageCache ()
#4 0x92f83458 in -[NSCachedImageRep window] ()
#5 0x92f83202 in -[NSImage _getCacheWindow:andRect:forRep:] ()
#6 0x9307fa8e in -[NSImage
TIFFRepresentationUsingCompression:factor:] ()
#7 0xcf13d7b4 in -[iMBMoviesView saveImageForPath:] (self=0xee42830,
_cmd=0xcf1528f6, imagePath=0xeef4e60) at /Development/Sources/
googlecode/imedia-nsview-branch/branch20080218/iMBMoviesView.m:225
*/
The creation code (two variants):
/* TE: work around an NSImageCache bug !?! */
[image setScalesWhenResized:YES];
[image setSize:newSize];
#if 0
NSData *tiffData = [image TIFFRepresentation];
NSBitmapImageRep *tiffRep = [NSBitmapImageRep
imageRepWithData:tiffData];
NSImage *newImage = [[NSImage allocWithZone:[self zone]]
initWithSize:newSize];
[newImage setScalesWhenResized:YES];
[newImage addRepresentation:tiffRep];
#else
NSImage *newImage = [[NSImage allocWithZone:[self zone]]
initWithSize:newSize];
[newImage setScalesWhenResized:YES];
[newImage setDataRetained:YES];
//? [newImage setCachedSeparately:YES];
[newImage lockFocus];
[image drawInRect:NSMakeRect(0.0f, 0.0f, newSize.width,
newSize.height)
fromRect:NSMakeRect(0.0f, 0.0f, size.width, size.height)
operation:NSCompositeCopy fraction:1.0f];
[newImage unlockFocus];
#endif
return [newImage autorelease];
Regards,
Tom_E
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