How to detect a Retina Mac
How to detect a Retina Mac
- Subject: How to detect a Retina Mac
- From: "Gerriet M. Denkmann" <email@hidden>
- Date: Sun, 18 Aug 2013 20:03:43 +0700
I just noticed that the program I use to create Png files creates files with twice the number of pixels in each dimension.
Obviously because since I last used it, I have switched to a Retina Mac Book.
Ok, so I have to fix this program.
But: how do I detect that the programm is running on a computer where each pixel is really four pixels?
Both NSScreen and NSWindow have a backingScaleFactor property, which seems to be right.
But my code does neither involves a screen nor a window:
finalWidth = 50; because I want a Png 50 pixels wide
finalWidth /= 2; ← this fixes my Retina problem, but hardcoding this looks simply wrong
CGFloat scaleFactor = finalWidth / bounds.size.width;
NSSize sizE = NSMakeSize( finalWidth, bounds.size.height * scaleFactor );
NSImage *image = [[NSImage alloc] initWithSize: sizE];
[image setFlipped:YES];
[image lockFocus];
NSGraphicsContext *currentContext = [NSGraphicsContext currentContext];
NSAffineTransform *transform = [NSAffineTransform transform];
[transform scaleXBy: scaleFactor yBy: scaleFactor ];
[transform translateXBy: -bounds.origin.x yBy: -bounds.origin.y ];
[transform concat];
... do some drawing
[image unlockFocus];
NSRect recct = NSMakeRect(0, 0, sizE.width, sizE.height );
[image lockFocus];
NSBitmapImageRep *bitmapImageRep = [[NSBitmapImageRep alloc] initWithFocusedViewRect: recct ];
[image unlockFocus];
NSData *data = [ bitmapImageRep representationUsingType: NSPNGFileType properties: nil ];
... write data to file
So where do I get my backingScaleFactor from?
What if there are two screens, one Retina, one not?
Kind regards,
Gerriet.
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