topic Re: Exporting the map image in ArcGIS Runtime SDK for iOS Questions

Exporting the map image

RickJones — Mon, 18 Jul 2011 17:22:38 GMT

Where would I look for a function to export the mapview's image?
I've tried the reference.

Re: Exporting the map image

NimeshJarecha — Fri, 10 Dec 2021 22:03:48 GMT

Rick,

There is no direct function in ArcGIS API for iOS to export image of mapView. You need to use iOS SDK to do so. It's very simple. Here is the code...

- (IBAction)exportMapViewImage:(id)sender {
 
 //export image of mapView
 UIGraphicsBeginImageContext(self.mapView.frame.size);
 [self.mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
 UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 
 //save image to photo album
 UIImageWriteToSavedPhotosAlbum(screenshot,self,@selector(image:didFinishSavingWithError:contextInfo:),nil);
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    // Was there an error?
    if (error != NULL)
    {
  // Show error message...
  UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error"
              message:[error localizedDescription]
                delegate:nil
             cancelButtonTitle:@"OK"
             otherButtonTitles:nil];
  [alert show];
  [alert release];
    }
    else  // No errors
    {
  // Show message image successfully saved
  UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Image Saved"
              message:@"Image saved to photo album successfully!"
                delegate:nil
             cancelButtonTitle:@"OK"
             otherButtonTitles:nil];
  [alert show];
  [alert release];
    }
}

Regards,
Nimesh

Re: Exporting the map image

RickJones — Wed, 20 Jul 2011 13:56:10 GMT

Nimesh,

Thank you for the snippet. I was unable to get it to work however.
I get "Error, Data unavailable" when it executes.

I don't see a property or method for AGSMapView called layer, but the compiler doesn't complain.
(I've tried 1.8 and 2.0).

I thought perhaps it was my Feature layers, so I created a new ViewDemo with Dynamic layer, and still got the error.

Re: Exporting the map image

NimeshJarecha — Wed, 20 Jul 2011 15:43:27 GMT

Looks like you're testing in Simulator. Try testing on device. The layer property of mapView is inherited property of UIView.

Send your project if you're unable to get it to work.

Regards,
Nimesh

Re: Exporting the map image

RickJones — Thu, 21 Jul 2011 13:18:04 GMT

Thank you, it does work on the device.
And now, it works on the simulator.

What's interesting is, the saved image shows gridlines for the Tiles, while the screen image doesn't.

Re: Exporting the map image

ChristopherEbright — Fri, 22 Jul 2011 13:27:01 GMT

Thanks Nimesh, that is a neat little trick.
I am going to try and extend that to export pdf to email.

Chris

Re: Exporting the map image

NimeshJarecha — Fri, 22 Jul 2011 20:03:00 GMT

Rick,

Glad to know that it works for you now. 🙂 Not sure why the grid lines coming in the image.

Chris,

You're welcome 🙂

Regards,
Nimesh

Re: Exporting the map image

BedaKuster — Wed, 17 Aug 2011 13:58:32 GMT

Did anyone find out how to make an image without gridlines?

Re: Exporting the map image

Nicholas-Furness — Fri, 10 Dec 2021 22:03:50 GMT

Hi all,

Took a little bit of sleuthing and reading up of Apple's documentation, but I did in the end manage to get rid of those pesky "grid lines". They're doubtless tile boundaries that aren't being drawn to the graphics context in the same way as to the screen. To me it smacked of some rounding during rendering, or anti-aliasing.

Sure enough, to get rid of them you need to add this line:

CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), NO);

However, you will notice if you're using a retina display, that the captured image is different to the on-screen one. To fix that, you need to begin the Image Context with some options other than the defaults adopted by UIGraphicsBeginImageContext().

This is some serious Apple silliness, but at least the documentation is there to guide you. So, use the following:

UIGraphicsBeginImageContextWithOptions(self.mapView.frame.size, NO, 0.0f);

By specifying a scale of 0.0f, you are telling the renderer to use the device's main display's resolution. On a retina display, you'd get the same effect if you used 2.0f, but 0.0f will work on any device.

You might also get away with YES instead of NO for the opaque parameter if you know enough about the layers you're rendering etc. etc..

So, the final code looks something like this:

UIGraphicsBeginImageContextWithOptions(self.mapView.frame.size, NO, 0.0f);
CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), NO);

[self.mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

//save image to photo album
UIImageWriteToSavedPhotosAlbum(screenshot,self,@selector(image:didFinishSavingWithError:contextInfo:),nil);

Hope this helps!

By the way, I still haven't got this to work in the simulator. Rick - do you remember how you got that to work?

Nick.

Re: Exporting the map image

RickJones — Thu, 18 Aug 2011 11:49:09 GMT

I spoke too soon. It no longer works in simulator. I get Data Unavailable now.

Re: Exporting the map image

Nicholas-Furness — Fri, 19 Aug 2011 00:07:04 GMT

OK, that's reassuring at least, because that's what I've always got and seems to be what Nimesh expected.

n

Re: Exporting the map image

BedaKuster — Fri, 19 Aug 2011 07:31:07 GMT

Thanks for the trick with antialiasing. By the way, same code works for me in (iPad-)simulator...

Re: Exporting the map image

RickJones — Fri, 19 Aug 2011 12:12:55 GMT

If anyone wants to implement a flash effect, here is my code:
(add a white, opaque, fullscreen view panel, zero alpha, over the mapView)

- (void)exportMapViewImage {
//export image of mapView
UIGraphicsBeginImageContextWithOptions(self.mapView.frame.size, NO, 0.0f);
CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), NO);

[self.mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// implement a flash
self.flashView.alpha = 1;
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.5];
self.flashView.alpha = 0;
[UIView commitAnimations];

//save image to photo album
UIImageWriteToSavedPhotosAlbum(screenshot,self,@selector(image:didFinishSavingWithError:contextInfo:),nil);
}