BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  TOpenPictureDialog and Large Images          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Pete Guest Posted: Tue Jun 01, 2004 4:08 pm    Post subject: TOpenPictureDialog and Large Images I am trying to avoid the problem where TOpenPictureDialog fails on files with large images, because of the well-known GDI limitations. At the same time, I am adding support for additional file formats (e.g. JPG, PNG), using a 3rd-party image library. I'm doing this by loading image files into a DIB, creating a thumbnail TBitmap of a "safe" size, then Assigning that to the TPicture being displayed. Calls to RegisterFileFormat tie it all together. This all works fine, even with images needing more than 100MB of memory, but I could use some help with loose ends: 1. How do I disable Delphi's built-in support for .BMP (and other) files, so that I can replace them with the above technique? 2. How do I get TOpenPictureDialog to display the pixel size of the original image, rather than the size of the thumbnail I'm actually displaying? 3. How can I make my changes only apply to TOpenPictureDialog, and not to other TPictures (where the use of a thumbnail may not be appropriate)? 4. How can I change the TOpenPictureDialog's cursor to crHourglass when loading large files? 5. How can I speed things up with very large files? They take for ever! TIA Pete Back to top Nils Haeck Guest Posted: Tue Jun 01, 2004 10:37 pm    Post subject: Re: TOpenPictureDialog and Large Images Answer to all questions: Create your own dialog, "TMyOpenPictureDialog". Nils "Pete" <nobody (AT) nowhere (DOT) com> wrote Quote: I am trying to avoid the problem where TOpenPictureDialog fails on files with large images, because of the well-known GDI limitations. At the same time, I am adding support for additional file formats (e.g. JPG, PNG), using a 3rd-party image library. I'm doing this by loading image files into a DIB, creating a thumbnail TBitmap of a "safe" size, then Assigning that to the TPicture being displayed. Calls to RegisterFileFormat tie it all together. This all works fine, even with images needing more than 100MB of memory, but I could use some help with loose ends: 1. How do I disable Delphi's built-in support for .BMP (and other) files, so that I can replace them with the above technique? 2. How do I get TOpenPictureDialog to display the pixel size of the original image, rather than the size of the thumbnail I'm actually displaying? 3. How can I make my changes only apply to TOpenPictureDialog, and not to other TPictures (where the use of a thumbnail may not be appropriate)? 4. How can I change the TOpenPictureDialog's cursor to crHourglass when loading large files? 5. How can I speed things up with very large files? They take for ever! TIA Pete Back to top Pete Guest Posted: Wed Jun 02, 2004 12:31 am    Post subject: Re: TOpenPictureDialog and Large Images On Wed, 2 Jun 2004 00:37:39 +0200, Nils Haeck wrote: Quote: Answer to all questions: Create your own dialog, "TMyOpenPictureDialog". Nils I was afraid you'd say that! If I limit myself to #1, is there an easier answer? i.e.: 1. How do I disable Delphi's built-in support for .BMP (and other) files, so that I can replace them with the above technique? Back to top Nils Haeck Guest Posted: Wed Jun 02, 2004 1:22 am    Post subject: Re: TOpenPictureDialog and Large Images Yes, it was a bit mean to say that was it :) Well, I think you can disable support for a format by calling TPicture.UnregisterGraphicsClass(). Then after that you can register it to your own handler of BMP, using TPicture.RegisterFileFormat(). However, you must do this *after* the graphics unit has registered it, so observe the unit loading sequence. Kind regards, Nils Haeck www.simdesign.nl "Pete" wrote in message news:10g0l0lbun24m$.vjbftu85a6i2.dlg (AT) 40tude (DOT) net... Quote: I was afraid you'd say that! If I limit myself to #1, is there an easier answer? i.e.: 1. How do I disable Delphi's built-in support for .BMP (and other) files, so that I can replace them with the above technique? Back to top willem van Deursen Guest Posted: Wed Jun 02, 2004 6:32 am    Post subject: Re: TOpenPictureDialog and Large Images The sourcecode of the OpenPictureDiolog is available in the delphi source folder. This code gives enough information to derive your own preview dialog, with dedicated support such as pixel size etc. Also, once inside this code, you can use standard techniques to display PNG etc. JPEG should be automatically supported once you add JPEG to the uses clause. PBPreviewDialog (available though www.torry.net and many others) offers a generic way of creating your own preview mechanisms, so might be worth exploring.... Willem Pete wrote: Quote: I am trying to avoid the problem where TOpenPictureDialog fails on files with large images, because of the well-known GDI limitations. At the same time, I am adding support for additional file formats (e.g. JPG, PNG), using a 3rd-party image library. I'm doing this by loading image files into a DIB, creating a thumbnail TBitmap of a "safe" size, then Assigning that to the TPicture being displayed. Calls to RegisterFileFormat tie it all together. This all works fine, even with images needing more than 100MB of memory, but I could use some help with loose ends: 1. How do I disable Delphi's built-in support for .BMP (and other) files, so that I can replace them with the above technique? 2. How do I get TOpenPictureDialog to display the pixel size of the original image, rather than the size of the thumbnail I'm actually displaying? 3. How can I make my changes only apply to TOpenPictureDialog, and not to other TPictures (where the use of a thumbnail may not be appropriate)? 4. How can I change the TOpenPictureDialog's cursor to crHourglass when loading large files? 5. How can I speed things up with very large files? They take for ever! TIA Pete -- Willem van Deursen, The Netherlands [email]wvandeursen_nospam (AT) nospam_carthago (DOT) nl[/email] replace _nospam@nospam_ for @ to get a valid email address www.carthago.nl Back to top Pete Guest Posted: Wed Jun 02, 2004 8:15 pm    Post subject: Re: TOpenPictureDialog and Large Images On Wed, 2 Jun 2004 03:22:11 +0200, Nils Haeck wrote: Quote: Well, I think you can disable support for a format by calling TPicture.UnregisterGraphicsClass(). Then after that you can register it to your own handler of BMP, using TPicture.RegisterFileFormat(). However, you must do this *after* the graphics unit has registered it, so observe the unit loading sequence. Thanks for the tip Nils, especially the "however...". You persuaded me to bite the bullet and write my own TOpenPictureDialogEx. All issues in my OP were easily resolved. 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