Re: Resizing NSimage

FROM : Yann Bizeul
DATE : Thu Nov 25 15:32:50 2004

> So to improve it, I'm looking at Cocoa functions and it seems possible
> to draw the image at different sizes. I guess I could use Quartz to
> draw to an offscreen image?? Then access that image.
> Before going down that path, any simpler / better
> suggestions...something like producing a resized bitmap directly from
> the original one...

Here is a code I use to resample an image, it produces good quality
thumbnails.
This is adapted from a sample found somewhere in the archives.

=== CUT HERE ===
    NSSize thumbSize = NSMakeSize(200,200);

    NSImage *tiff = [[NSImage alloc]initWithContentsOfFile:[self
valueForKey:@"file"]];

    float bigRatio = [tiff size].width / [tiff size].height;
    float thumbRatio = thumbSize.width / thumbSize.height;

    NSSize smallSize;
    if (bigRatio > thumbRatio)
       smallSize = NSMakeSize(thumbSize.width,thumbSize.width/bigRatio);
    else
       smallSize = NSMakeSize(thumbSize.height*bigRatio,thumbSize.height);

    NSBitmapImageRep *imageRepA = [[tiff
representations]objectAtIndex:0];
    NSBitmapImageRep *imageRep = [imageRepA representationWithSize:
smallSize];

    NSDictionary *properties = [NSDictionary dictionaryWithObject:
[NSNumber numberWithFloat: 1.0] forKey: NSImageCompressionFactor];

    [[imageRep representationUsingType:NSJPEGFileType
properties:properties]writeToFile:outJPEGFile atomically:YES];
=== CUT HERE ===


This rely on a NSBitmapImageRep category :
------------------------------------------

=== CUT HERE ===
@implementation NSBitmapImageRep (Sizing)
- (NSBitmapImageRep *)representationWithSize:(NSSize)size
{
    NSRect rect = NSMakeRect(0, 0, size.width, size.height);
    NSImage *image = [[[NSImage alloc] initWithSize:size] autorelease];
    NSBitmapImageRep *outRep;
    [image lockFocus];
    [[NSGraphicsContext
currentContext]setImageInterpolation:NSImageInterpolationHigh];
    [self drawInRect:rect];
    outRep = [[[NSBitmapImageRep alloc] initWithFocusedViewRect:rect]
   autorelease];
    [image unlockFocus];
    return outRep;
}
@end
=== CUT HERE ===

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Yann Bizeul - yann at tynsoe.org
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