XnView Software

Posted: **Tue Jul 18, 2006 9:19 pm**

Hi experts,

as i have resize speed problems with the Delphi's TImage, i tried to test with the gflResizeCanvas as used in the Visual Basic sample "Form 10".

First i needed to adapt the VB code (i can read it only, because i cannot make it run with VB5) to Delphi; centered along the VB functions (plus helpers)
extGetGflBitmapFromPtr and extShowBitmapOnDc
for to test if i can display my (good) gfl_bmp (PGFL_BITMAP) via those functions (based on a GFL_BITMAP resp. TGFL_BITMAP object) on an Delphi TImage.

I adapted those functions so far, but the result image resp. device context ... is simply white.
Is there anybody who can help to track this down resp. has a working adaption of "extShowBitmapOnDc" resp. gflResizeCanvas for Delphi?

More general, is this approach (by going the fast DIB-way [extShowBitmapOnDc uses StretchDIBits)) the recommed way to react on resize actions on the user interface? (does xnview itself do so?)

Many thanks and best regards,
klaus2

Posted: **Wed Jul 19, 2006 5:12 pm**

I succeeded to adapt the VB functios extGetGflBitmapFromPtr and extShowBitmapOnDc
(From VB example gflResizeCanvas.frm) to Delphi, but i have 2 problems with it; see below.
Many thanks for any clues in advance!

If i can fix those problems, i expect that i can do a fast image resize reacting of user change of the window size, using gflResizeCanvas and modifying the DestRect of the StretchDIBits. Am i right?

Best Regards,
klaus2

Prob 1: the output image flipped vertically by 180 degrees (top is bottom and vice versa);
obviously dib-specific (built up upside down); possible solutions without loosing too much speed?
(btw the VB sample does _not_ show the image flipped)

Prob 2: access violation with gflMemoryFree in extGetGflBitmapFromPtr

Code: Select all

procedure extGetGflBitmapFromPtr(src: Pointer; var dest: TGFL_BITMAP);
var pdest: PGFL_BITMAP;
begin
    pdest :=  @dest;    // address of dest
    gflFreeBitmapData(pdest);
    CopyMemory(pdest, src, SizeOf(TGFL_BITMAP));
    gflMemoryFree(src);   // <--- Access violation here (on Delphi6/Win2K only, not with D4/Win98)
end;

The function is called like: extGetGflBitmapFromPtr(Pointer(pgfl_bmp), gfl_bmp);
where "src" resp. "pgfl_bmp" is defined as an instance variable of the Form as: pgfl_bmp: PGFL_BITMAP;
it's retrieved from the gflLoadBitmap.

Posted: **Wed Jul 19, 2006 6:04 pm**

About the vertical flip of the DIB derived image, i can fix it with
"loadparams.Origin := GFL_BOTTOM_LEFT;" for the gflLoadBitmap,
but - ouch! - that's ugly because i need an original windows Bitmap object too
fron the gflLoadBitmap (as of Delphi sample code) .... and now, of course, that one would be flipped.
Some way around?

XnView Software

Question about gflResizeCanvas / VB sample with Delphi

Question about gflResizeCanvas / VB sample with Delphi