Load PDF into layer offscreen

Question

Is there a way to load a PDF into a CALayer (or CATiledLayer) offscreen and then just display it when required? The solution should also support zooming at the required resolution.

Update
Just to clarify - I want the pdf to remain vector based.

Answer 1

Note : you told that You need to load PDF into CALayer. But Here, I have the solution for loading entire pdf pages into images. Once images are in an array, you can view any of them as & when required. Add comment if you have any doubts.

• You just have to copy & paste following code. It will almost work for you. I have tested.

First of all put following method above the implementation of your view controller.

NSMutableArray *aRefImgs; // global variable.
void setRefImgs(NSMutableArray *ref){
    aRefImgs=ref;
}

NSMutableArray* ImgArrRef(){
    return aRefImgs;
}
CGPDFDocumentRef MyGetPDFDocumentRef (const char *filename) {
    CFStringRef path;
    CFURLRef url;
    CGPDFDocumentRef document;
    path = CFStringCreateWithCString (NULL, filename,kCFStringEncodingUTF8);
    url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, 0);
    CFRelease (path);
    document = CGPDFDocumentCreateWithURL (url);// 2
    CFRelease(url);
    int count = CGPDFDocumentGetNumberOfPages (document);// 3
    if (count == 0) {
        printf("`%s' needs at least one page!", filename);
        return NULL;
    }
    return document;
}

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

Now, place following code in your viewController.m file.

-(void)viewDidLoad {
    filePath=[[NSString alloc] initWithString:[[NSBundle mainBundle] pathForResource:@"roadie" ofType:@"pdf"]];

    CGPDFDocumentRef d=MyGetPDFDocumentRef([filePath UTF8String]);

    size_t nos=CGPDFDocumentGetNumberOfPages(d); 
    totalPages=nos;
    arrImgs=[[NSMutableArray alloc] init]; // arrImgs variable declared in viewController.h file.
setRefImgs(arrImgs);
int i;
for(i=0;i<nos;i++){
    UIGraphicsBeginImageContext(CGSizeMake(720, 720));
    MyDisplayPDFPage(UIGraphicsGetCurrentContext(), i+1, [filePath UTF8String],myTable,mainString);
    UIImage *tmp=UIGraphicsGetImageFromCurrentImageContext();
    UIImage *t2=[tmp rotate:UIImageOrientationDownMirrored];
    [arrPDFImgs addObject:t2];
    UIImageView *imgV=[[UIImageView alloc] initWithFrame:CGRectMake(scrPDFImages.frame.size.width * i, 0, scrPDFImages.frame.size.width, scrPDFImages.frame.size.height)];
    [imgV setContentMode:UIViewContentModeScaleToFill];
    [imgV setImage:t2];
    [scrPDFImages addSubview:imgV]; 
            // scrPDFImages is an array that has all images 
            // per page one image from pdf document
    [imgV release];
    UIGraphicsPopContext();
    }
}

You might need image orientation - i also have placed entire class here.

@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