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114 lines
3.9 KiB
Objective-C
114 lines
3.9 KiB
Objective-C
// Created by Scott Stevenson on 9/28/07.
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//
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// Personal site: http://theocacao.com/
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// Post for this sample: http://theocacao.com/document.page/497
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//
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// The code in this project is intended to be used as a learning
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// tool for Cocoa programmers. You may freely use the code in
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// your own programs, but please do not use the code as-is in
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// other tutorials.
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#import "NSImageAdditions.h"
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@implementation NSImage (Extras)
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- (NSImage*)imageByScalingProportionallyToSize:(NSSize)targetSize
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{
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NSImage* sourceImage = self;
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NSImage* newImage = nil;
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if ([sourceImage isValid])
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{
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NSSize imageSize = [sourceImage size];
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CGFloat width = imageSize.width;
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CGFloat height = imageSize.height;
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CGFloat targetWidth = targetSize.width;
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CGFloat targetHeight = targetSize.height;
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// scaleFactor will be the fraction that we'll
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// use to adjust the size. For example, if we shrink
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// an image by half, scaleFactor will be 0.5. the
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// scaledWidth and scaledHeight will be the original,
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// multiplied by the scaleFactor.
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//
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// IMPORTANT: the "targetHeight" is the size of the space
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// we're drawing into. The "scaledHeight" is the height that
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// the image actually is drawn at, once we take into
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// account the ideal of maintaining proportions
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CGFloat scaleFactor = 0.0;
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CGFloat scaledWidth = targetWidth;
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CGFloat scaledHeight = targetHeight;
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NSPoint thumbnailPoint = NSMakePoint(0,0);
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// since not all images are square, we want to scale
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// proportionately. To do this, we find the longest
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// edge and use that as a guide.
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if ( NSEqualSizes( imageSize, targetSize ) == NO )
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{
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// use the longeset edge as a guide. if the
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// image is wider than tall, we'll figure out
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// the scale factor by dividing it by the
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// intended width. Otherwise, we'll use the
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// height.
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CGFloat widthFactor = targetWidth / width;
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CGFloat heightFactor = targetHeight / height;
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if ( widthFactor < heightFactor )
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scaleFactor = widthFactor;
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else
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scaleFactor = heightFactor;
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// ex: 500 * 0.5 = 250 (newWidth)
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scaledWidth = width * scaleFactor;
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scaledHeight = height * scaleFactor;
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// center the thumbnail in the frame. if
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// wider than tall, we need to adjust the
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// vertical drawing point (y axis)
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if ( widthFactor < heightFactor )
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thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
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else if ( widthFactor > heightFactor )
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thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
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}
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// create a new image to draw into
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newImage = [[NSImage alloc] initWithSize:targetSize];
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// once focus is locked, all drawing goes into this NSImage instance
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// directly, not to the screen. It also receives its own graphics
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// context.
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//
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// Also, keep in mind that we're doing this in a background thread.
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// You only want to draw to the screen in the main thread, but
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// drawing to an offscreen image is (apparently) okay.
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[newImage lockFocus];
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NSRect thumbnailRect;
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thumbnailRect.origin = thumbnailPoint;
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thumbnailRect.size.width = scaledWidth;
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thumbnailRect.size.height = scaledHeight;
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[sourceImage drawInRect: thumbnailRect
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fromRect: NSZeroRect
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operation: NSCompositeSourceOver
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fraction: 1.0];
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[newImage unlockFocus];
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}
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return [newImage autorelease];
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}
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@end |