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Exporting the map image

RickJones

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

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NimeshJarecha

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

RickJones

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.

NimeshJarecha

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

RickJones

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.

ChristopherEbright

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

Chris

NimeshJarecha

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

BedaKuster

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

Nicholas-Furness

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.

RickJones

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

Nicholas-Furness

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

n

BedaKuster

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

RickJones

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);
}

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