Merge pull request #142 from mortonfox/patch-2

Update link to Instruments

Author: mallorypaine

README.md

@@ -74,7 +74,7 @@ Consider the workflow that occurs when loading an image from disk and displaying
 
 <sup>1</sup> `60FPS` ≈ `0.01666s per frame` = `16.7ms per frame`. This means that any main-thread work that takes longer than 16ms will cause your application to drop animation frames.
 
-<sup>2</sup> The documentation for [`CALayer`](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCwQFjAA&url=https%3A%2F%2Fdeveloper.apple.com%2Flibrary%2Fios%2Fdocumentation%2Fgraphicsimaging%2Freference%2FCALayer_class%2FIntroduction%2FIntroduction.html&ei=P29XUpj2LeahiALptICgCQ&usg=AFQjCNGwJuHcQV4593kuookUcvNZYTvx5w&sig2=zi1audY4ZsNE_xLeESVD_Q)'s [`contents`](https://developer.apple.com/library/ios/documentation/graphicsimaging/reference/CALayer_class/Introduction/Introduction.html#//apple_ref/doc/uid/TP40004500-CH1-SW24) property states that "assigning a value to this property causes the layer to use your image rather than [creating] a separate backing store." However, the meaning of "use your image" is still vague. Profiling an application using [Instruments](https://developer.apple.com/library/ios/documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40004652-CH1-SW1) often reveals calls to `CA::Render::copy_image`, even when the Core Animation Instrument has indicated that none of the images have been copied. One reason that Core Animation will require a copy of an image is improper [byte alignment](#byte-alignment). 
+<sup>2</sup> The documentation for [`CALayer`](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCwQFjAA&url=https%3A%2F%2Fdeveloper.apple.com%2Flibrary%2Fios%2Fdocumentation%2Fgraphicsimaging%2Freference%2FCALayer_class%2FIntroduction%2FIntroduction.html&ei=P29XUpj2LeahiALptICgCQ&usg=AFQjCNGwJuHcQV4593kuookUcvNZYTvx5w&sig2=zi1audY4ZsNE_xLeESVD_Q)'s [`contents`](https://developer.apple.com/library/ios/documentation/graphicsimaging/reference/CALayer_class/Introduction/Introduction.html#//apple_ref/doc/uid/TP40004500-CH1-SW24) property states that "assigning a value to this property causes the layer to use your image rather than [creating] a separate backing store." However, the meaning of "use your image" is still vague. Profiling an application using [Instruments](https://developer.apple.com/library/prerelease/content/documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/) often reveals calls to `CA::Render::copy_image`, even when the Core Animation Instrument has indicated that none of the images have been copied. One reason that Core Animation will require a copy of an image is improper [byte alignment](#byte-alignment). 
 
 <sup>3</sup> As of iOS 7, Apple does not make their hardware JPEG decoder available for third-party applications to use. As a result, only a slower, software decoder is used for this step.