How to override draw method on PDFAnnotation IOS-PDFKIT

问题

I followed another StackOverflow post that explains how i could override the draw method of a PDFAnnotation so i could draw a picture instead of a traditional PDFAnnotation.

But sadly i was not able to achieve that and the annotation that is drawn on top of my pdf is still a regular one.

This is the code that i used :

@implementation PDFImageAnnotation { UIImage * _picture;
                            CGRect _bounds;};


-(instancetype)initWithPicture:(nonnull UIImage *)picture bounds:(CGRect) bounds{
    self = [super initWithBounds:bounds
                  forType:PDFAnnotationSubtypeWidget
                  withProperties:nil];

    if(self){
        _picture = picture;
        _bounds = bounds;
    }
    return  self;
}


- (void)drawWithBox:(PDFDisplayBox) box
          inContext:(CGContextRef)context {
    [super drawWithBox:box inContext:context];
    [_picture drawInRect:_bounds];
    
    CGContextRestoreGState(context);
    UIGraphicsPushContext(context);
    
};

@end

Does someone know how i could override the draw method so i could draw a custom Annotation ?

Thank You !

ps: i also tried to followed the tutorial on the apple dev site.

UPDATE :

Now i'm able to draw pictures using CGContextDrawImage but i'm not able to flip coordinates back in place. when i do that mi pictures are not drawn and it seems that they are put outside of the page but i'm not sure.

This is my new code :

- (void)drawWithBox:(PDFDisplayBox) box
          inContext:(CGContextRef)context {
    [super drawWithBox:box inContext:context];
    
    UIGraphicsPushContext(context);
    CGContextSaveGState(context);
    
    
    CGContextTranslateCTM(context, 0.0, _pdfView.bounds.size.height);
    CGContextScaleCTM(context, 1.0,  -1.0);
    
    CGContextDrawImage(context, _bounds, _picture.CGImage);


    CGContextRestoreGState(context);
    UIGraphicsPopContext();
}

回答1:

I also tried to follow the tutorial on the Apple dev site.

Which one?

• Custom Graphics
• Adding Custom Graphics to a PDF

Because both include UIGraphicsPushContext(context) & CGContextSaveGState(context) calls, but your code doesn't. Do not blindly copy & paste examples, try to understand them. Read what these two calls do.

Fixed code:

- (void)drawWithBox:(PDFDisplayBox) box
          inContext:(CGContextRef)context {
    [super drawWithBox:box inContext:context];
    
    UIGraphicsPushContext(context);
    CGContextSaveGState(context);
    
    [_picture drawInRect:_bounds];

    CGContextRestoreGState(context);
    UIGraphicsPopContext();
}

The image was drawn with CGRectMake(20, 20, 100, 100). It's upside down, because PDFPage coordinates are flipped (0, 0 = bottom/left). Leaving it as an exercise for OP.

Rotation

Your rotation code is wrong:

CGContextTranslateCTM(context, 0.0, _pdfView.bounds.size.height);
CGContextScaleCTM(context, 1.0,  -1.0);
    
CGContextDrawImage(context, _bounds, _picture.CGImage);

It's based on _pdfView bounds, but it should be based on the image bounds (_bounds). Here's the correct one:

- (void)drawWithBox:(PDFDisplayBox) box
          inContext:(CGContextRef)context {
    [super drawWithBox:box inContext:context];
    
    UIGraphicsPushContext(context);
    CGContextSaveGState(context);

    CGContextTranslateCTM(context, _bounds.origin.x, _bounds.origin.y + _bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    [_picture drawInRect:CGRectMake(0, 0, _bounds.size.width, _bounds.size.height)];

    CGContextRestoreGState(context);
    UIGraphicsPopContext();
}

来源：https://stackoverflow.com/questions/63283248/how-to-override-draw-method-on-pdfannotation-ios-pdfkit