title: iOS OpenGLES 2.0 blending differences between iOS 9 and iOS 10
body: <p>I am implementing normal UIKit-like blending using textures with transparency in OpenGLES 2.</p>
  
  <p>On iOS 9.3.5 blending works correct on iPad mini for textures with premultiplied alpha and following blend function:</p>
  
  <pre><code>glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
  </code></pre>
  
  <p>On iOS 10.3.1 blending works correct on iPad Air for textures with non-premultiplied alpha and the same blend function.</p>
  
  <p>Textures are loaded via this line:</p>
  
  <pre><code>[glkTextureLoader textureWithContentsOfFile:path 
           options: @{ GLKTextureLoaderApplyPremultiplication : @NO /* @YES here for iOS 9 */ }
          queue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)
          completionHandler:^(GLKTextureInfo * _Nullable textureInfo, 
                                     NSError * _Nullable outError) {
                                                                      ...
                                                                   }
  </code></pre>
  
  <p>What can cause such differences in rendering?</p>