Returns the image transparency type, which will be one of <code>SWT.TRANSPARENCY_NONE</code>, <code>SWT.TRANSPARENCY_MASK</code>, <code>SWT.TRANSPARENCY_PIXEL</code> or <code>SWT.TRANSPARENCY_ALPHA</code>.
@return the receiver's transparency type
See Implementation
Returns the image transparency type, which will be one of <code>SWT.TRANSPARENCY_NONE</code>, <code>SWT.TRANSPARENCY_MASK</code>, <code>SWT.TRANSPARENCY_PIXEL</code> or <code>SWT.TRANSPARENCY_ALPHA</code>.
@return the receiver's transparency type