Question

The code is pretty easy, it has to load from a settings file all the existing images references, scale them to 250×250 and save them with another name.

The problem is that on the device (tested on an iPhone 3g and an iPad) it crashes after a while with memory warnings. On the simulator it’s working perfect.

I have a UIViewController which has on ViewDidAppear this code:

ThreadPool.QueueUserWorkItem( delegate{ 
    make_thumbs(); 
}); 

The make_thumbs function is:

void make_thumbs() 
{ 
    using( var ns = new NSAutoreleasePool() ) 
    { 
        foreach( var c in Settings.Instance.Categories ) 
        { 
            for( var i = 0; i < c.Pictures.Count; i++ ) 
            { 
                //this is the existing bundled image path 
                string     path = c.Pictures[i].PicturePath; 
                string   folder = Environment.GetFolderPath( Environment.SpecialFolder.Personal ); 
                //this is the destination image file name 
                string filename = Path.Combine( folder, c.Name + i + ".png"); 
                if( !File.Exists( filename ) ) 
                { 
                    NSError err;
                    using(UIImage img = UIImage.FromFile( path ).Scale( 250,250 ))
                    {
                        img.AsPNG().Save( filename, true, out err );
                    }
                } 
            } 
        } 
    } 
}

Answer 1

Thx @poupou, it was almost good your answer, with a little completion: i had to put the
using( var ns = new NSAutoreleasePool() ) inside the for loop. So my code is now like this and it’s working:

if( !File.Exists( filename ) )
{
    using( var ns = new NSAutoreleasePool() )
    {
        NSError err;
        using(UIImage img = UIImage.FromFile( path )) {
            using (var scaled_img = img.Scale( 250,250 )) 
            {
                //i also add a reflection effect                             
                using( var reflected_img = scaled_img.AddImageReflection( 0.6f ) )
                {
                    using (var data = reflected_img.AsPNG ()) 
                    {
                        data.Save( filename, true, out err );
                    }
                }
             }
        }
    }
}