IDL 8.2: Change in behavior when using 3-D arrays for button icons on Windows

IDL widget buttons can be labeled using images. To do this, you can provide the WIDGET_BUTTON function with a bitmap file, a 4-D array, or a 3-D array.  In IDL 8.2, the behavior of the WIDGET_BUTTON function has changed when a 3-D array is used to generate the label on Windows systems. For example, in IDL 8.1, you can enter in the following code into IDL and it will create a button that has three boxes (colored red, green and blue) on  a black background:

test_img = BYTARR(100,100,3)
test_img[25:50,25:50,1]=255
test_img[0:25,0:25,0]=255
test_img[50:75,50:75,2]=255

base=WIDGET_BASE() ;create the widget base
button=WIDGET_BUTTON(base,VALUE=test_img)  ;create the widget button
widget_control,base,/REALIZE

However, If you are using IDL 8.2 on Windows, you will notice that the box in the bottom left corner is colored grey (it should be colored red).

                   

 Caption: Left picture: button as it would appear in IDL8.1 (the color is correct).
Right picture: button as it appear in IDL 8.2 (bottom corner grayed out).

There are three methods you could use to get the color to display correctly:

1) You can set the MASK keyword with the WIDGET_BUTTON to zero. By default the Mask keyword of the WIDGET_BUTTON is set to 1. On Windows, this makes the pixel value in the bottom left-hand corner of the image transparent. If you set MASK=0, it removes the gray from the image:

base=WIDGET_BASE() ;create the widget base
button=WIDGET_BUTTON(base,VALUE=test_img, MASK=0)  ;create the widget button
widget_control,base,/REALIZE

2) Change the value in the lower left pixel to a color that is not used anywhere else in the image. For example, you could add the "test_img[ 0, 0, 0 ] = 254" before creating the button in the example code.

3) You can convert the 3-D array (RGB) to a 4-D array (RGBA) with the alpha values all set to 255. For example:

test_img = BYTARR(100,100,3)
test_img[25:50,25:50,1]=255
test_img[0:25,0:25,0]=255
test_img[50:75,50:75,2]=255


;get the version information
vers = !version.RELEASE
vers = float(vers)


if (vers gt 8.1) then begin ;check if version is IDL 8.2

     temp_img=BYTARR(100,100,4)
     temp_img[0,0,0]=test_img
     temp_img[*,*,3]=255
     test_img=temp_img

endif


base=WIDGET_BASE() ;create the widget base
button=WIDGET_BUTTON(base,VALUE=test_img)  ;create the widget button
widget_control,base,/REALIZE