iOS: Generate PDF from UIView makes text blurry - objective-c

Question

Generate PDF from UIView by rendering looses quality iOS
I have a custom UIView called TTT_WantsToBeRazorSharpView.
This view does nothing, but draw a text with
NSString*txtPleaseHelp = NSLocalizedString(#"Hello, am I blurry again?",#"");
CGContextShowTextAtPoint(ctx, 10, 50, [txtPleaseHelp cStringUsingEncoding:NSMacOSRomanStringEncoding], [txtPleaseHelp length]);
Now the View is drawn three times to an UIViewController (one time in IB) and two times in code with these lines (compare to image below):
TTT_WantsToBeRazorSharpView *customViewSharp = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:CGRectMake(10,250, 300, 80)];
[self.view addSubview:customViewSharp];
TTT_WantsToBeRazorSharpView *customViewBlurryButIKnowWhy = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:CGRectMake(361.5, 251.5, 301.5, 80.5)];
[self.view addSubview:customViewBlurryButIKnowWhy];
the first code drawn view is razorsharp, while the second isn't, but that is ok, because of rect's comma values (361.5, 251.5, 301.5, 80.5).
See this picture:
But my problem is now, if I render the view into an pdf document it is blurry!
And don't know why, see here:
and the PDF file itself Test.pdf
https://raw.github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality/master/Test.pdf
and the lines to render the view into the pdf:
//this is blurry, but why? it can't be the comma coordinates
CGRect customFrame1 = CGRectMake(10,50, 300, 80);
TTT_WantsToBeRazorSharpView *customViewSharp = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:customFrame1];
CGContextSaveGState(context);
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, (int)customFrame1.origin.x, (int)customFrame1.origin.y);
[customViewSharp.layer renderInContext:context];
CGContextRestoreGState(context);
So why is the renderInContext:context text blurry?
I appreciate all your hints and help, I even made an GitHub project for the brave of you (with source): https://github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality

Answer 1

Try this:
- (void)initValues {
UIColor *gray = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.3f];
CALayer *l = [self layer];
l.masksToBounds = YES;
l.cornerRadius = 10.0f;
l.borderWidth = 3.0f;
self.backgroundColor = gray;
l.backgroundColor = gray.CGColor;
l.borderColor = gray.CGColor;
}
- (void)drawRect:(CGRect)rect {
NSLog(#"TTT_WantsToBeRazorSharpView drawRect[%3.2f,%3.2f][%3.2f,%3.2f]",rect.origin.x,rect.origin.y,rect.size.width,rect.size.height);
// get the graphic context
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetShouldSmoothFonts(ctx,YES);
CGColorRef colorWhite = CGColorRetain([UIColor redColor].CGColor);
CGContextSetFillColorWithColor(ctx, colorWhite);
CGContextSelectFont(ctx, "Helvetica-Bold", 24, kCGEncodingMacRoman);
CGAffineTransform tranformer = CGAffineTransformMakeScale(1.0, -1.0);
CGContextSetTextMatrix(ctx, tranformer);
//why is this sucker blurry?
NSString*txtPleaseHelp = NSLocalizedString(#"Hello, am I blurry again?",#"");
CGContextShowTextAtPoint(ctx, 10, 50, [txtPleaseHelp cStringUsingEncoding:NSMacOSRomanStringEncoding], [txtPleaseHelp length]);
CGColorRelease(colorWhite);
}
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
if (!layer.shouldRasterize && !CGRectIsEmpty(UIGraphicsGetPDFContextBounds())) {
[self drawRect:self.bounds];
}
else {
[super drawLayer:layer inContext:ctx];
}
}
I had to change the text color to red to make it visible. Because the text is written first, then the transparent grey button is placed over it, it would make the white text disappear. When adding the drawLayer method, everything that does not need to be rasterized is written as vector to pdf, making the text also selectable.

Answer 2

The text in the view is rendered as bitmap in the PDF and not as vector graphics and this causes the blurry appearance. My guess is iOS rendering engine draws the text on an intermediary bitmap (for color composition purposes I think) and then this bitmap is rendered on the target context.

Answer 3

I have used the following command to fix blurry text:
self.frame = CGRectIntegral(self.frame);
The reason for blurry text was that alignment was not ideal, i.e. fraction values in the point coordinates, so the text appear blurry due to excessive antialiasing.