objective-c - iOS:从 UIView 生成 PDF 使文本模糊

Question

通过渲染质量不佳的 iOS 从 UIView 生成 PDF

我有一个名为 TTT_WantsToBeRazorSharpView 的自定义 UIView。 这个 View 什么都不做，只是用

绘制文本

NSString*txtPleaseHelp = NSLocalizedString(@"Hello, am I blurry again?",@"");
CGContextShowTextAtPoint(ctx, 10, 50, [txtPleaseHelp cStringUsingEncoding:NSMacOSRomanStringEncoding], [txtPleaseHelp length]);

现在 View 被绘制三次到 UIViewController(一次在 IB 中)，两次在代码中使用这些行(与下图比较):

 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];

第一个代码绘制的 View 非常清晰，而第二个则不是，但没关系，因为 rect 的逗号值 (361.5, 251.5, 301.5, 80.5)。

看这张图:

但我现在的问题是，如果我将 View 渲染成 pdf 文档，它会变得模糊! 不知道为什么，请看这里:

和 PDF 文件本身 Test.pdf https://raw.github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality/master/Test.pdf

以及将 View 渲染成 pdf 的行:

//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);

那么为什么 renderInContext:context 文本模糊不清？

感谢您的所有提示和帮助，我什至为勇敢的您创建了一个 GitHub 项目(带源代码):https://github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality

Answer 1

试试这个:

- (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];
    }
}

我不得不将文本颜色更改为红色以使其可见。因为文字是先写的，然后透明的灰色按钮放在上面，它会使白色文字消失。添加 drawLayer 方法时，所有不需要栅格化的内容都写为矢量到 pdf，使文本也可以选择。