message: Improvements for performance-related headsup in debug mode
diff: @@ -136,6 +136,7 @@ assert!(subimg.dimensions() == (100, 100));
  ## Image Processing Functions
  These are the functions defined in the `imageops` module. All functions operate on types that implement the `GenericImage` trait.
  +Note that some of the functions are very slow in debug mode. Make sure to use release mode if you experience any performance issues.
  + **blur**: Performs a Gaussian blur on the supplied image.
  + **brighten**: Brighten the supplied image.
  @@ -147,7 +148,7 @@ These are the functions defined in the `imageops` module. All functions operate
  + **flip_vertical**: Flip an image vertically.
  + **grayscale**: Convert the supplied image to grayscale.
  + **invert**: Invert each pixel within the supplied image This function operates in place.
  -+ **resize**: Resize the supplied image to the specified dimensions. Note that this is very slow in debug mode. Make sure to use release mode when using this.
  ++ **resize**: Resize the supplied image to the specified dimensions.
  + **rotate180**: Rotate an image 180 degrees clockwise.
  + **rotate270**: Rotate an image 270 degrees clockwise.
  + **rotate90**: Rotate an image 90 degrees clockwise.
  