iOS - 通过渲染从 UIView 生成 PDF 会降低质量

我使用以下方法从 UIView 生成 PDF。它们都创建了 PDF，但质量下降了：

方法一：

@implementation UIView(PDFWritingAdditions)

- (void)renderInPDFFile:(NSString*)path
{
    CGRect mediaBox = self.bounds;
    CGContextRef ctx = CGPDFContextCreateWithURL((__bridge_retained CFURLRef)[NSURL fileURLWithPath:path], &mediaBox, NULL);
    CGPDFPageRef page;
    CGContextDrawPDFPage(ctx, page);

    CGPDFContextBeginPage(ctx, NULL);

    // Also tried following commented lines but no luck
    //    CGContextSetFlatness(ctx, 0.1);
    //    CGContextSetAllowsAntialiasing(ctx, YES);
    //    CGContextSetAllowsFontSmoothing(ctx, YES);
    //    CGContextSetInterpolationQuality(ctx, kCGInterpolationHigh);
    CGContextScaleCTM(ctx, 1, -1);
    CGContextTranslateCTM(ctx, 0, -mediaBox.size.height);
    [self.layer renderInContext:ctx];
    CGPDFContextEndPage(ctx);
    CFRelease(ctx);
}

@end

方法二：

- (void)createPDFfromUIView:(UIView*)aView saveToDocumentsWithFileName:(NSString*)aFilename
{
    // Creates a mutable data object for updating with binary data, like a byte array
    NSMutableData *pdfData = [NSMutableData data];

    // Points the pdf converter to the mutable data object and to the UIView to be converted
    UIGraphicsBeginPDFContextToData(pdfData, aView.bounds, nil);
    UIGraphicsBeginPDFPage();
    CGContextRef pdfContext = UIGraphicsGetCurrentContext();


    // draws rect to the view and thus this is captured by UIGraphicsBeginPDFContextToData

    [aView.layer renderInContext:pdfContext];

    // remove PDF rendering context
    UIGraphicsEndPDFContext();

    // Retrieves the document directories from the iOS device
    NSArray* documentDirectories = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);

    NSString* documentDirectory = [documentDirectories objectAtIndex:0];
    NSString* documentDirectoryFilename = [documentDirectory stringByAppendingPathComponent:aFilename];

    // instructs the mutable data object to write its context to a file on disk
    [pdfData writeToFile:documentDirectoryFilename atomically:YES];
    NSLog(@"documentDirectoryFileName: %@",documentDirectoryFilename);
}

我想我可能缺少 pdf 上下文的一些设置，不确定。我还使用以下方法从 UIView 创建了 png 图像，其质量完全相同：

- (UIImage *)imageFromView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    // Retrieves the document directories from the iOS device
    NSArray* documentDirectories = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);

    NSString* documentDirectory = [documentDirectories objectAtIndex:0];
    NSString* documentDirectoryFilename = [documentDirectory stringByAppendingPathComponent:@"pdf.png"];

    // instructs the mutable data object to write its context to a file on disk
    [UIImagePNGRepresentation(img) writeToFile:documentDirectoryFilename atomically:YES];
    NSLog(@"documentDirectoryFileName: %@",documentDirectoryFilename);
    return img;
}

有人能看到我做错了什么吗？ 谢谢。

这是使用视网膜显示器吗？这可能是一个 contentScale 的事情。看一下这个帖子 https://stackoverflow.com/questions/4334233/how-to-capture-uiview-to-uiimage-without-loss-of-quality-on-retina-display

EDIT好的，现在您已经发布了前后照片，我看到您希望发票 UIView 在 PDF 中呈现为漂亮、高质量、可打印的矢量数据。

我非常确定 [CALayer renderInContext] 始终会生成光栅数据，因此您最好手动构建 PDF。如果您谈论的是税务发票，您真的希望布局随着下一个 iOS 更新而改变吗？

然而，你可以看看这个答案 https://stackoverflow.com/questions/7509999/ios-create-pdf-from-uiview，它不情愿地建议使用 UIView 作为 PDF 布局的模板系统。