格式转换：如何将CGPDFPageRef转换为CGImageRef

http://blog.sina.com.cn/s/blog_7ccde1bf0100ysi2.html

 

以下Carbon代码可以将PDF页面CGPDFPageRef转换为Quartz的CGImageRef格式，这样就可以将PDF页面用在Core Animation中了。

 CGImageRef PDFPageToCGImage(size_t pageNumber, CGPDFDocumentRef document)

{

CGPDFPageRefpage;

CGRectpageSize;

CGContextRefoutContext;

CGImageRefThePDFImage;

CGAffineTransformctm;

page = CGPDFDocumentGetPage (document, pageNumber);

if(page)

{

pageSize =CGPDFPageGetBoxRect(page,kCGPDFMediaBox);

outContext= CreateARGBBitmapContext (pageSize.size.width, pageSize.size.height);

if(outContext)

{

CGContextDrawPDFPage(outContext, page);

ThePDFImage= CGBitmapContextCreateImage(outContext);

CFRelease(outContext);

return ThePDFImage;  

}

}

returnNULL;

} 

 

//From apple:http://developer.apple.com/qa/qa2007/qa1509.html

 

CGContextRef CreateARGBBitmapContext (size_t pixelsWide, size_t pixelsHigh)

{

    CGContextRef    context = NULL;

    CGColorSpaceRef colorSpace;

    void *          bitmapData;

    int             bitmapByteCount;

    int             bitmapBytesPerRow;

// Get image width, height. We’ll use the entire image.

 //  size_t pixelsWide = CGImageGetWidth(inImage);

 //  size_t pixelsHigh = CGImageGetHeight(inImage);

   // Declare the number of bytes per row. Each pixel in the bitmap in this

   // example is represented by 4 bytes; 8 bits each of red, green, blue, and

   // alpha.

    bitmapBytesPerRow   = (pixelsWide * 4);

    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

   // Use the generic RGB color space.

    colorSpace =CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);

    if (colorSpace == NULL)

    {

        fprintf(stderr, "Error allocating color space\n");

        returnNULL;

    }

   // Allocate memory for image data. This is the destination in memory

   // where any drawing to the bitmap context will be rendered.

    bitmapData = malloc( bitmapByteCount );

    if (bitmapData == NULL)

    {

        fprintf (stderr, "Memory not allocated!");

CGColorSpaceRelease( colorSpace );

        returnNULL;

    }

   // Create the bitmap context. We want pre-multiplied ARGB, 8-bits

   // per component. Regardless of what the source image format is

   // (CMYK, Grayscale, and so on) it will be converted over to the format

   // specified here by CGBitmapContextCreate.

    context = CGBitmapContextCreate (bitmapData,

pixelsWide,

pixelsHigh,

8,      // bits per component

bitmapBytesPerRow,

colorSpace,

kCGImageAlphaPremultipliedFirst);

    if (context == NULL)

    {

        free (bitmapData);

        fprintf (stderr, "Context not created!");

    }

   // Make sure and release colorspace before returning

    CGColorSpaceRelease( colorSpace );

    return context;

}