If LegacyBitmap is True, ImageEn uses TBitmap to store the image, otherwise ImageEn uses TIEBitmap. TIEBitmap handles images using memory mapped file (for large images) or main memory. This allows handling of large images and to include input/output and image processing in a multi-threaded environment. Also TIEBitmap supports a larger number of pixel formats (TIEPixelFormat) than TBitmap (TPixelFormat).
So as I understand, it is best to set LegacyBitmap to False for your large PSD images so they are loaded as a memory mapped TIEBitmap. You should get better performance and less memory problems because the images are memory mapped. Large image IO can also be improved by compiling your application as Win64 because more memory will be available. Compiling as 64bit is simple. Just add the ielib64.dll to the exe folder. Image loading will also be about 30% faster than with Win32bit.
When you set LegacyBitmap to False all references to ImageEnView.Bitmap will be nil. As a result you can not access TBitmap properties. So if LegacyBitmap is False and you try to access Bitmap an exception will be produced. In this case use IEBitmap to access the image.
For example:
{ Use TIEBitmap to handle images using memory mapped file (for large images) or main memory by setting LegacyBitmap to False } ImageEnView.LegacyBitmap := False; { An exception will occur in the next line because Bitmap is nil} ImageEnView.Bitmap.Modified := False;
To get a TBitmap instead of an TIEBitmap when LegacyBitmap is False use ImageEnView.IEBitmap.VclBitmap.
So you must use a global var instead to track if a IEBitmap has been modified or use the ImageEnView.IEBitmap.VclBitmap.Modified property.
The nice part of setting ImageEnView.LegacyBitmap := True is you can access both the TBitmap or TIEBitmap properties. So both TBitmap and TIEBitmap properties will be valid and both will contain a valid graphic and will not nil.
Having said this, Nigel or Fabrizio probably can offer better guidance than I, and make any corrections to my comments.
It seems I should go with LegacyMode set to False.
Actually I do not have any need to access the Modified property. But to change over from LecacyMode would mean changing my code heavily as I have used TBitmape at quite a lot of places.
But if setting this mode to false do yield better performance then I am ready to do this also.
Anybody more practical experience on this? Please share your views.
Many of the demos were created prior to the TIEBitmap functionality so they default to LegacyMode = true. With your new projects you should almost always set LegacyMode to false.
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Why LegacyBitmap is always True?
Posted - Dec 28 2013 : 03:26:17
