Re: changing brightness and contrast in an nsimage
Re: changing brightness and contrast in an nsimage
- Subject: Re: changing brightness and contrast in an nsimage
- From: Kenny Leung <email@hidden>
- Date: Sat, 3 Dec 2005 22:02:56 -0800
I've been wondering why this is so difficult, and I think that the
answer is that all of this stuff is meant to be done in the display
pipeline. If you want the bits back, you can probably use -[CIContext
createCGImage:fromRect:]. If you are in the NSImage world, you can
render into an NSImage and pull back the bits by creating an
NSBitmapImageRep from the NSImage data:
image = [[NSImage alloc] initWithSize:NSMakeSize(width, height)];
[image lockFocus];
[[NSGraphicsContext currentContext]
setImageInterpolation:NSImageInterpolationHigh];
[[self adjustedImage] drawInRect:NSMakeRect(0, 0, width, height)
fromRect:NSMakeRect(0, 0, [self image_width], [self image_height])
operation:NSCompositeCopy fraction:1.0];
imageRep = [[NSBitmapImageRep alloc]
initWithFocusedViewRect:NSMakeRect(0, 0, width, height)];
[image unlockFocus];
data = [imageRep representationUsingType:NSJPEG2000FileType
properties:nil];
-Kenny
On Dec 3, 2005, at 9:39 PM, Eric Smith wrote:
OK... I've gone to the CIImage.
Next question: I can create a CIImage from NSBitmapImagRep, but
all I can get from the CIImage is an NSImageRep... this has no
method for getting at the bitmap data. Once I'm using a CIImage,
how do I get the bitmap data?
Thanks again,
Eric
On Dec 3, 2005, at 7:30 PM, Dave Camp wrote:
I think the problem is it isn't clear what you are asking for...
Are you asking for pointers to general brightness and contrast
algorithms?
Are you asking how to get at the NSImage bitmap data to manipulate
it yourself?
Or are you asking if there are other Apple supplied frameworks
that will perform brightness and contrast adjustments for you?
Dave
On Dec 3, 2005, at 8:04 PM, Eric Smith wrote:
CIImage wasn't even around until 10.4... there must be a way to
handle this from an NSImage. Anyone out there use brightness and
contrast controls on an NSImage, or the bitmap data associated
with the NSImage?
Thanks,
Eric
On Dec 2, 2005, at 9:34 PM, John C. Randolph wrote:
On Dec 2, 2005, at 9:29 PM, Eric Smith wrote:
I've been going around in circles with this one...
What is a good way to change the brightness and contrast in an
NSImage?
I've been playing with the vImage library for changing
contrast, using the vImageEndsInContrastStretch. This works,
but how does one return the contrast to it's original value?
Once you specify that > 0% of the pixels lie at the histogram
extreme, you can't get the original values back. I know of the
ImagApp example showing how to use CIImage, but using that
would require a re-write of quite a bit of code... I'd rather
not go there.
Too bad, because that's how to do it.
-jcr
John C. Randolph <email@hidden> (408) 914-0013
Roaming Cocoa Engineer,
Available for your projects at great Expense and Inconvenience.
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