在位图上下文中呈现的CFGPDF质量差

Question

有没有办法将PDF页面渲染到位图上下文而不会降低质量？

这是我的代码：

-(UIImage *)imageForPage:(int)pageNumber sized:(CGSize)size{

    CGPDFDocumentRef _document  = [self CreatePDFDocumentRef:filePath];
    CGPDFPageRef page = CGPDFDocumentGetPage (_document, pageNumber);


    CGRect pageRect = CGPDFPageGetBoxRect(page,kCGPDFTrimBox);
    CGSize pageSize = pageRect.size;
    pageSize = MEDSizeScaleAspectFit(pageSize, size);

    UIGraphicsBeginImageContextWithOptions(pageSize, NO, 0.0);

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    CGContextSetRenderingIntent(context, kCGRenderingIntentDefault);

    CGContextTranslateCTM(context, 0.0, pageSize.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextSaveGState(context);

    CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFTrimBox, CGRectMake(0, 0, pageSize.width, pageSize.height), 0, true);
    CGContextConcatCTM(context, pdfTransform);
    CGContextDrawPDFPage(context, page);
    CGContextRestoreGState(context);

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGPDFDocumentRelease (_document);
    return resultingImage;
}


CGSize MEDSizeScaleAspectFit(CGSize size, CGSize maxSize) {
    CGFloat originalAspectRatio = size.width / size.height;
    CGFloat maxAspectRatio = maxSize.width / maxSize.height;
    CGSize newSize = maxSize;
    // The largest dimension will be the `maxSize`, and then we need to scale
    // the other dimension down relative to it, while maintaining the aspect
    // ratio.
    if (originalAspectRatio > maxAspectRatio) {
        newSize.height = maxSize.width / originalAspectRatio;
    } else {
        newSize.width = maxSize.height * originalAspectRatio;
    }

    return newSize;
}

Answer 1

确保您创建的图像接近等于其显示的尺寸。这将创建一个最准确显示的图像。