Confused about NSImageView scaling

cocoa nsimageview
betzerra picture betzerra · Dec 6, 2012 · Viewed 8.4k times · Source

I'm trying to display a simple NSImageView with it's image centered without scaling it like this:

Just like iOS does when you set an UIView's contentMode = **UIViewContentModeCenter**

Just like iOS does when you set an UIView's contentMode = UIViewContentModeCenter

So I tried all NSImageScaling values, this is what I get when I chose NSScaleNone

I really don't understand what's going on :-/

I really don't understand what's going on :-/

Answer

Shagru picture Shagru · Aug 5, 2013

You can manually generate the image of the correct size and content, and set it to be the image of the NSImageView so that NSImageView doesn't need to do anything.

NSImage *newImg = [self resizeImage:sourceImage size:newSize];
[aNSImageView setImage:newImg];

The following function resizes an image to fit the new size, keeping the aspect ratio intact. If the image is smaller than the new size, it is scaled up and filled with the new frame. If the image is larger than the new size, it is downsized, and filled with the new frame

- (NSImage*) resizeImage:(NSImage*)sourceImage size:(NSSize)size{

NSRect targetFrame = NSMakeRect(0, 0, size.width, size.height);
NSImage*  targetImage = [[NSImage alloc] initWithSize:size];

NSSize sourceSize = [sourceImage size];

float ratioH = size.height/ sourceSize.height;
float ratioW = size.width / sourceSize.width;

NSRect cropRect = NSZeroRect;
if (ratioH >= ratioW) {
    cropRect.size.width = floor (size.width / ratioH);
    cropRect.size.height = sourceSize.height;
} else {
    cropRect.size.width = sourceSize.width;
    cropRect.size.height = floor(size.height / ratioW);
}

cropRect.origin.x = floor( (sourceSize.width - cropRect.size.width)/2 );
cropRect.origin.y = floor( (sourceSize.height - cropRect.size.height)/2 );



[targetImage lockFocus];

[sourceImage drawInRect:targetFrame
               fromRect:cropRect       //portion of source image to draw
              operation:NSCompositeCopy  //compositing operation
               fraction:1.0              //alpha (transparency) value
         respectFlipped:YES              //coordinate system
                  hints:@{NSImageHintInterpolation:
 [NSNumber numberWithInt:NSImageInterpolationLow]}];

[targetImage unlockFocus];

return targetImage;}

Related questions

Mac OS Cocoa: Draw a simple pixel on a canvas

I wish I would find an answer for this. I have searched and searched and couldn't the right answer. Here is my situation: In a Mac OS Cocoa Application, I want to draw a pixel (actually a few pixels) onto …

Read More
Setting an image on NSImageView

I'm having a problem with my program. Basically what i want is, i have 2 nssecuretextfield and i have a button. if both are equal, it shows one image on the nsimageview, if not it displays other image. This could be …

Read More
mouseEntered and mouseExited not called in NSImageView SubClass

I created a subclass of NSImageView to capture mouseEntered and mouseExited events. But only mouseUp and mouseDown events are getting called. How to capture the mouseEntered and mouseExited events in NSImageView subclass?

Read More