Hi Ken,
Actually, the -[NSImage lockFocus]/-[NSImage unlockFocus] were added
to deal with a multi-thread problem that was deadlocking things. If a
background thread updated screen state while I was creating the RGB
image representation, I would later see a message in the console log
reading "unlockFocus called too many time.", and threads would start
deadlocking.
I changed things around a bit, and am now calling lockFocus on
rgbImage instead - simply to avoid the multi-thread issue. It seems
to be working.
Thanks for your time,
Ron Aldrich
Software Architects, Inc.
On Feb 13, 2009, at 1:41 PM, Ken Ferry wrote:
Hi Ron,
It was the -[NSImage lockFocus]/-[NSImage unlockFocus] that did it.
You should just take them out, they weren't relevant to what you
were trying to do.
-[NSImage lockFocus] sets the receiver up as a drawing
_destination_. You aren't trying to draw into the image here,
you're trying to draw _from_ it.
lockFocus will
(1) Create a buffer.
(2) Make the buffer the current drawing graphics context, so that
methods like NSRectFill are directed to the buffer.
(3) Draw the existing contents of the image into the new buffer.
unlockFocus will
(4) pop the current graphics context back to whatever it was before
lockFocus was called.
(5) take the contents of the buffer and make them the new contents
of the image.
In particular, lockFocus/unlockFocus is necessarily destructive.
The old image representations are discarded, replaced with a new one.
-Ken
On Thu, Feb 12, 2009 at 5:52 PM, Ron Aldrich <raldr...@mac.com> wrote:
Folks,
I'm having an issue where CMYK images aren't being recognized by my
quartz compositions, so I need to convert them to RGB for display.
I've written a routine to do it, but its causing problems.
NSImageRep* theImageRep = [inputImage bestRepresentationForDevice:
[NSDictionary dictionaryWithObject: NSDeviceRGBColorSpace
forKey
: NSDeviceColorSpaceName]];
NSString* theColorSpace = [theImageRep colorSpaceName];
if ([theColorSpace isEqualToString: NSDeviceCMYKColorSpace])
{
NSBitmapImageRep* theRGBImageRep = [[[NSBitmapImageRep alloc]
initWithBitmapDataPlanes: NULL
pixelsWide
: [theImageRep pixelsWide]
pixelsHigh
: [theImageRep pixelsHigh]
bitsPerSample
: 8
samplesPerPixel
: 4
hasAlpha
: YES
isPlanar
: NO
colorSpaceName
: NSDeviceRGBColorSpace
bytesPerRow
: 0
bitsPerPixel
: 0] autorelease];
[inputImage lockFocus];
NSGraphicsContext* theContext = [NSGraphicsContext
graphicsContextWithBitmapImageRep: theRGBImageRep];
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext: theContext];
NSRect theBoundsRect = NSMakeRect(0.0, 0.0, [theRGBImageRep
pixelsWide], [theRGBImageRep pixelsHigh]);
[[NSColor clearColor] set];
NSRectFill(theBoundsRect);
[theImageRep drawInRect: theBoundsRect];
[NSGraphicsContext restoreGraphicsState];
[inputImage unlockFocus];
ASSIGNOBJECT(rgbImage, [[[NSImage alloc] initWithSize:
[theImageRep size]] autorelease]);
[rgbImage addRepresentation: theRGBImageRep];
}
else
{
ASSIGNOBJECT(rgbImage, inputImage);
}
The resulting image is correct, but somewhere along the line, my
original image (inputImage) is being modified - the CMYK
representation is being removed, and replaced with a downsampled RGB
representation. The goal here was to leave inputImage unmodified,
so that when it is finally sent to the printer, the CMYK
representation would be used.
inputImage before creating the RGB version.
NSImage 0x12313dd0 Size={340.08, 340.08} Reps=(
NSBitmapImageRep 0xd8201c0 Size={340.08, 340.08}
ColorSpace=NSDeviceCMYKColorSpace BPS=8 BPP=32 Pixels=1417x1417
Alpha=NO Planar=NO Format=0
)
inputImage after creating the RGB version.
NSImage 0x12313dd0 Size={340.08, 340.08} Reps=(
NSCachedImageRep 0xd824530 Size={340, 340}
ColorSpace=NSCalibratedRGBColorSpace BPS=8 Pixels=340x340 Alpha=NO
)
Clearly, I'm doing something wrong. I added calls to [inputImage
lockFocus] and [inputImage unlockFocus] in order to resolve a multi-
thread problem, but that seems to have caused this problem.
So, what's the best way for me to convert an NSImage of unknown
pedigree to a simple RGB representation?
Thanks,
Ron Aldrich
Software Architects, Inc.
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