Image Processing Toolbox Release Notes

Upgrading from an Earlier Release

This section describes several upgrade issues involved in moving from the Image Processing Toolbox Version 3.1 to Version 3.2.

Change to Data Type of Output Binary Images

All the Image Processing Toolbox functions that return a binary image now return a binary image of class logical. In previous releases, these functions returned binary images of a numeric class with the logical flag set. The Image Processing Toolbox used the existence of the logical flag to identify a binary image.

If your application checks the data type of the binary images returned by Image Processing Toolbox functions, you will need to change your code.

Note    The logical class is not one of the numeric classes in MATLAB.

Change to Interpretation of Input Images

Image Processing Toolbox functions that accept different types of images, such as grayscale and binary, no longer attempt to determine if an input image of a numeric class is intended to be a binary image.

In previous releases, toolbox functions that acccepted different types of images checked the contents of an image to determine how to interpret it. For example, if an image was of class double and contained only 0s and 1s, the toolbox function would interpret it as a binary image. With Version 3.2, the toolbox only interprets images of class logical as binary images.

In the Image Processing Toolbox, the names of functions that accept both grayscale and binary images typically start with the characters "im", such as imdilate.

Converting Binary Images to an Integer Data Type

With this release, if you convert a binary image to a numeric type, the image ceases to be a binary image.

In previous releases, the Image Processing Toolbox conversion functions im2uint8 and im2double preserved the binary attribute of the converted image. For example, if you converted a binary image of class double, which had the logical flag set, the output image returned by the im2uint8 function would also be a logical image of class uint8, with the logical flag set.

For example, create a simple logical array

• bw = logical([1 0; 0 1])
  bw =
  
       1     0
       0     1
  whos
  Name           Size                   Bytes  Class
  
  bw             2x2                        4  logical array
  

When you convert this array to a uint8 data type, notice that it is no longer of class logical.

• new_image = im2uint8(bw)
  
  new_image =
  
     255     0
       0   255
  
  whos
  Name           Size                   Bytes  Class
  
  bw               2x2                      4  logical array
  new_image        2x2                      4  uint8 array
  

Major Bug Fixes

Image Processing Toolbox 3.1 Release Notes