This is a wild guess but it worked for me with Core Text on the iPad a long
time ago. One or several of these can probably work for you.
• CGContextSetAllowsAntialiasing
• CGContextSetAllowsFontSmoothing
• CGContextSetShouldSmoothFonts
• CGContextSetAllowsFontSubpixelPositioning
• CGContextSetShouldSubpixelPositionFonts
• CGContextSetAllowsFontSubpixelQuantization
• CGContextSetShouldSubpixelQuantizeFonts
-ev
On Apr 27, 2011, at 12:45, Simone Manganelli wrote:
> I'm adding some Core Animation to my existing project, and I'm encountering
> some differences in the font rendering compared to non-Core Animation code.
> Here's the code used to draw my strings:
>
>> NSShadow *selectedShadow = [[NSShadow alloc] init];
>> [selectedShadow setShadowOffset:NSMakeSize(0,-1)];
>> [selectedShadow setShadowColor:[NSColor colorWithCalibratedWhite:0.0
>> alpha:0.33]];
>> [selectedShadow autorelease];
>>
>> NSMutableParagraphStyle *leftAlignedEllipsisStyle =
>> [[NSMutableParagraphStyle alloc] init];
>> [leftAlignedEllipsisStyle setAlignment:NSLeftTextAlignment];
>> [leftAlignedEllipsisStyle setLineBreakMode:NSLineBreakByWordWrapping];
>> [leftAlignedEllipsisStyle autorelease];
>>
>> NSDictionary *selectedAttributes = [NSDictionary
>> dictionaryWithObjectsAndKeys:
>> [NSFont systemFontOfSize:11.0],
>> NSFontAttributeName,
>> [NSColor whiteColor],
>> NSForegroundColorAttributeName,
>> selectedShadow, NSShadowAttributeName,
>> leftAlignedEllipsisStyle,
>> NSParagraphStyleAttributeName,
>> nil];
>>
>> [someString drawWithRect:textRect
>> options:NSStringDrawingTruncatesLastVisibleLine |
>> NSStringDrawingUsesLineFragmentOrigin
>> attributes:selectedAttributes];
>
> Here's the difference:
> http://homepage.mac.com/simx/images/antialiasing-diff.png
>
> On the left is text rendered in my existing project using the above code via
> the drawRect: method. On the right is text rendered into a CALayer using the
> drawLayer:inContext: method.
>
> I'm aware of the fact that Core Animation disables sub-pixel rendering for
> text when drawing to transparent backgrounds, so I've intentionally designed
> my CALayers so that they have opaque backgrounds. Sub-pixel rendering is
> definitely active now that I've drawn an opaque color to the layer. This
> doesn't seem to be the issue, especially because the Core Animation text
> appears *heavier* than the normal Quartz text, whereas it usually appears
> more wispy when sub-pixel rendering is off.
>
> Nor does this seem to be an issue with half-pixels. The selection bubble is
> rendering crisply (from image assets), which indicates that the layer is
> positioned correctly. And the text itself isn't blurred, so the text is also
> positioned correctly.
>
> This almost looks as if a heavier kind of antialiasing is active on the text.
> I recall that Mac OS X had four different types of antialiasing you could
> choose in the Appearance preference pane, but this preference is gone in more
> recent versions. Could I be hitting that and somehow using some different
> form of antialiasing?
>
> Any help would be greatly appreciated.
>
> -- Simone
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