Hi,
I'm trying to ensure that when a user elects to zoom the view (in this case a
PDFView) to actual size, that it shows the actual size on-screen as best it
can. I'm really close, but not quite all the way there. I tested the same
function in the Preview app, and there it works perfectly. When I zoom to
actual size, and hold a sheet of paper (of the same size as the PDF page) to
the screen, then they match perfectly. When I do the same in my app (which uses
the system provided PDFView), the on-screen page is ever so slightly smaller
than the physical page (say roughly 2mm).
This is the code in its current state:
#define MILLIMETERS_TO_POINTS_FACTOR 2.834645669
- (IBAction)zoomToActualSize:(id)sender
{
NSDictionary *screenDescription = [self.previewCanvas.window.screen
deviceDescription];
NSInteger screenID = [[screenDescription objectForKey:@"NSScreenNumber"]
integerValue];
NSSize pixelSize = [[screenDescription objectForKey:@"NSDeviceSize"]
sizeValue];
CGSize displaySize = CGDisplayScreenSize((CGDirectDisplayID)screenID); //
Returns size in mm
displaySize.width *= MILLIMETERS_TO_POINTS_FACTOR; // So convert into points
CGFloat factor = pixelSize.width / displaySize.width; // (Shouldn't matter
whether you calculate the factor by width or by height)
[self.previewCanvas setScaleFactor:factor];
}
Is there a way to improve on this? Apple must be doing something at least
slightly different to achieve virtually perfect results.
-António
-----------------------------------------
Forgiveness is not an occasional act;
it is a permanent attitude.
--Martin Luther King, Jr
-----------------------------------------
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