On Oct 9, 2014, at 8:05 PM, Ken Thomases <k...@codeweavers.com> wrote:
> On Oct 9, 2014, at 9:08 PM, Carl Hoefs <newsli...@autonomy.caltech.edu> wrote:
>
>> I need to scale an NSImage's dimensions to exactly 640x480 pixels before
>> sending it remotely for processing.
>
>> What is the correct way to do this?
>
> Create an NSBitmapImageRep with the appropriate properties. Create an
> NSGraphicsContext from that bitmap image rep using +[NSGraphicsContext
> graphicsContextWithBitmapImageRep:]. Make that graphics context current.
> Draw the image. Flush and restore the graphics context. Get the data from
> the bitmap image rep in an image file format using
> -representationUsingType:properties: or (if you really want TIFF)
> -TIFFRepresentationUsingCompression:factor:.
Awesome pointers, I got it to work! The tricky part was the actual scaling. It
would crop but not scale, so resorted to using CIImage. If there’s a cleaner
way, please let me know!
NSRect imgRect = NSMakeRect(0.0, 0.0, 640.0, 480.0);
NSSize imgSize = imgRect.size;
NSBitmapImageRep *offscreenRep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:NULL
pixelsWide:imgSize.width
pixelsHigh:imgSize.height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bitmapFormat:NSAlphaFirstBitmapFormat
bytesPerRow:8*4*imgSize.width
bitsPerPixel:32];
// set offscreen context
NSGraphicsContext *gc = [NSGraphicsContext
graphicsContextWithBitmapImageRep:offscreenRep];
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:gc];
// scale the image from cgRect down to imgRect
CIImage *ciImage = [CIImage imageWithData:dataObj];
CGRect cgRect = [ciImage extent];
[[gc CIContext] drawImage:ciImage inRect:imgRect fromRect:cgRect];
// reset the current context
[NSGraphicsContext restoreGraphicsState];
// create an NSImage and add the rep to it
NSImage *img = [[NSImage alloc] initWithSize:imgSize];
[img addRepresentation:offscreenRep];
NSLog(@"* Final Image: %@",img);
* Final Image: <NSImage 0x608000276c80 Size={640, 480} Reps=(
"NSBitmapImageRep 0x6080000b6b00 Size={640, 480} ColorSpace=(not yet
loaded) BPS=8 BPP=(not yet loaded) Pixels=640x480 Alpha=NO Planar=NO
Format=(not yet loaded) CurrentBacking=nil (faulting)
CGImageSource=0x608000167200"
)>
Thanks again!
-Carl
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