问iPad视网膜显示是否有办法减少CGContextBeginPage创建的文件大小？

EN

+(NSMutableData *)createPDFDatafromUIView:(UIView*)aView 
{
    // 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();

    return pdfData;
}

+(NSString*)createPDFfromUIView:(UIView*)aView saveToFilepath:(NSString*)filepath
{
    // Creates a mutable data object for updating with binary data, like a byte array
    NSMutableData *pdfData = [AppGraphics createPDFDatafromUIView:aView];


    // instructs the mutable data object to write its context to a file on disk
    [pdfData writeToFile:filepath atomically:YES];
    DLog(@"saving PDF to: %@",filepath);
    DLog(@"file exists: %@",[[NSFileManager defaultManager] fileExistsAtPath:filepath]?@"YES":@"NO");
    return filepath;
}

+ (NSString *)joinPDF:(NSArray *)listOfPaths saveToPath:(NSString*)path
{


    CFURLRef pdfURLOutput = (  CFURLRef)CFBridgingRetain([NSURL fileURLWithPath:path]);

    NSInteger numberOfPages = 0;
    // Create the output context
    CGContextRef writeContext = CGPDFContextCreateWithURL(pdfURLOutput, NULL, NULL);

    for (NSString *source in listOfPaths) {
        CFURLRef pdfURL = (  CFURLRef)CFBridgingRetain([[NSURL alloc] initFileURLWithPath:source]);

        //file ref
        CGPDFDocumentRef pdfRef = CGPDFDocumentCreateWithURL((CFURLRef) pdfURL);
        numberOfPages = CGPDFDocumentGetNumberOfPages(pdfRef);

        // Loop variables
        CGPDFPageRef page;
        CGRect mediaBox;

        // Read the first PDF and generate the output pages
        DLog(@"GENERATING PAGES FROM PDF 1 (%@)...", source);
        for (int i=1; i<=numberOfPages; i++) {
            page = CGPDFDocumentGetPage(pdfRef, i);
            mediaBox = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
            CGContextBeginPage(writeContext, &mediaBox);
            CGContextDrawPDFPage(writeContext, page);
            CGContextEndPage(writeContext);
        }

        CGPDFDocumentRelease(pdfRef);
        CFRelease(pdfURL);
    }
    CFRelease(pdfURLOutput);

    // Finalize the output file
    CGPDFContextClose(writeContext);
    CGContextRelease(writeContext);

    return path;
}