iPhone 某些 PDF 呈现为黑色图像

Question

我正在尝试使用下面的代码绘制 PDF 页面。某些 PDF 可以正确渲染，但其他 PDF 则仅显示为全黑图像，或者渲染了部分部分而其余部分为黑色。在比较所发生的情况时，显示“正常”的那些似乎总是包含“常规”文本以及一些图形(图表等)，而显示为黑色的通常都是图形(例如一页纸)例如音乐)。谁能指出我在这方面的正确方向？我在新的 3.2 SDK 上构建它。

谢谢!

// PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system
// before we start drawing.
 CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
 CGContextScaleCTM(context, 1.0, -1.0);

 // Grab the first PDF page
CGPDFPageRef page = CGPDFDocumentGetPage(myPDF, pageNo);
// We're about to modify the context CTM to draw the PDF page where we want it, so save     the graphics state in case we want to do more drawing
CGContextSaveGState(context);
// CGPDFPageGetDrawingTransform provides an easy way to get the transform for a PDF page. It will scale down to fit, including any
// base rotations necessary to display the PDF page correctly. 
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, self.bounds, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
// Finally, we draw the page and restore the graphics state for further manipulations!
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);

Answer 1

CGPDFDocumentRef MyGetPDFDocumentRef (const char *文件名) { CFStringRef 路径； CFURL引用网址； CGPDFDocumentRef 文档； 路径 = CFStringCreateWithCString (NULL, 文件名,kCFStringEncodingUTF8); url = CFURLCreateWithFileSystemPath (NULL, 路径, kCFURLPOSIXPathStyle, 0); CFRelease(路径)； 文档 = CGPDFDocumentCreateWithURL(url);//2 CFRelease(url); int count = CGPDFDocumentGetNumberOfPages (文档);//3 如果(计数==0){ printf("`%s' 至少需要一页!", 文件名); 返回空值； } 返回文件； }

void MyDisplayPDFPage (CGContextRef myContext,size_t pageNumber,const char *filename) {
    CGPDFDocumentRef document;
    CGPDFPageRef page;
    document = MyGetPDFDocumentRef (filename);// 1
    page = CGPDFDocumentGetPage (document, pageNumber);// 2
    CGContextDrawPDFPage (myContext, page);// 3
    CGContextTranslateCTM(myContext, 0, 20);
    CGContextScaleCTM(myContext, 1.0, -1.0);
    CGPDFDocumentRelease (document);// 4
}



#import "DashBoard.h"

#import <QuartzCore/QuartzCore.h>

@interface UIImage (WBImage)
// rotate UIImage to any angle
-(UIImage*)rotate:(UIImageOrientation)orient;
@end

@implementation UIImage (WBImage)


static inline CGFloat degreesToRadians(CGFloat degrees)
{
    return M_PI * (degrees / 180.0);
}

static inline CGSize swapWidthAndHeight(CGSize size)
{
    CGFloat  swap = size.width;

    size.width  = size.height;
    size.height = swap;

    return size;
}


-(UIImage*)rotate:(UIImageOrientation)orient
{
    CGRect             bnds = CGRectZero;
    UIImage*           copy = nil;
    CGContextRef       ctxt = nil;
    CGRect             rect = CGRectZero;
    CGAffineTransform  tran = CGAffineTransformIdentity;

    bnds.size = self.size;
    rect.size = self.size;

    switch (orient)
    {
        case UIImageOrientationUp:
            return self;

        case UIImageOrientationUpMirrored:
            tran = CGAffineTransformMakeTranslation(rect.size.width, 0.0);
            tran = CGAffineTransformScale(tran, -1.0, 1.0);
            break;

        case UIImageOrientationDown:
            tran = CGAffineTransformMakeTranslation(rect.size.width,
                                                    rect.size.height);
            tran = CGAffineTransformRotate(tran, degreesToRadians(180.0));
            break;

        case UIImageOrientationDownMirrored:
            tran = CGAffineTransformMakeTranslation(0.0, rect.size.height);
            tran = CGAffineTransformScale(tran, 1.0, -1.0);
            break;

        case UIImageOrientationLeft:
            bnds.size = swapWidthAndHeight(bnds.size);
            tran = CGAffineTransformMakeTranslation(0.0, rect.size.width);
            tran = CGAffineTransformRotate(tran, degreesToRadians(-90.0));
            break;

        case UIImageOrientationLeftMirrored:
            bnds.size = swapWidthAndHeight(bnds.size);
            tran = CGAffineTransformMakeTranslation(rect.size.height,
                                                    rect.size.width);
            tran = CGAffineTransformScale(tran, -1.0, 1.0);
            tran = CGAffineTransformRotate(tran, degreesToRadians(-90.0));
            break;

        case UIImageOrientationRight:
            bnds.size = swapWidthAndHeight(bnds.size);
            tran = CGAffineTransformMakeTranslation(rect.size.height, 0.0);
            tran = CGAffineTransformRotate(tran, degreesToRadians(90.0));
            break;

        case UIImageOrientationRightMirrored:
            bnds.size = swapWidthAndHeight(bnds.size);
            tran = CGAffineTransformMakeScale(-1.0, 1.0);
            tran = CGAffineTransformRotate(tran, degreesToRadians(90.0));
            break;

        default:
            // orientation value supplied is invalid
            assert(false);
            return nil;
    }

    UIGraphicsBeginImageContext(bnds.size);
    ctxt = UIGraphicsGetCurrentContext();

    switch (orient)
    {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            CGContextScaleCTM(ctxt, -1.0, 1.0);
            CGContextTranslateCTM(ctxt, -rect.size.height, 0.0);
            break;

        default:
            CGContextScaleCTM(ctxt, 1.0, -1.0);
            CGContextTranslateCTM(ctxt, 0.0, -rect.size.height);
            break;
    }

    CGContextConcatCTM(ctxt, tran);
    CGContextDrawImage(ctxt, rect, self.CGImage);

    copy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return copy;
}


@end




@implementation DashBoard

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
    filePath=[[NSString alloc] initWithString:[[NSBundle mainBundle] pathForResource:@"roadie" ofType:@"pdf"]];

    // an IBOutlet UIScrollView
    [scrMain setContentSize:CGSizeMake(720, 720)];
    // an IBOutlet UIImageView
    [imgV setFrame:CGRectMake(0, 0, 720, 720)];
    UIGraphicsBeginImageContext(CGSizeMake(720, 720));
    // initial page is an size_t variable
    initialPage=1;
    MyDisplayPDFPage(UIGraphicsGetCurrentContext(), initialPage, [filePath UTF8String],myTable,mainString);
    imgV.image=UIGraphicsGetImageFromCurrentImageContext();
    imgV.image=[imgV.image rotate:UIImageOrientationDownMirrored];
}

只需复制并粘贴上面的代码即可。它会对你有用。