BUG: StretchBlt()/StretchDIBits() Fail with Very Large Stretch (111865)
The information in this article applies to:
- Microsoft Windows Software Development Kit (SDK) for Windows 3.0
- Microsoft Windows Software Development Kit (SDK) for Windows 3.1
This article was previously published under Q111865
3.00 3.10
WINDOWS
kbprg kbbuglist
SYMPTOMS
If the stretching factor is large, for example, when stretching from a very
small to a large height, StretchDIBits() and StretchBlt() may return zero (0) and display nothing. The same bitmap with a smaller stretch is displayed correctly.
CAUSE
Most display drivers do not implement their own StretchBlt() or
StretchDIBits() so GDI must simulate these calls. Part of the GDI
simulation involves allocating temporary work buffers, which are limited to
64K. If the size of the work buffer is calculated to be greater than 64K,
then the height of the source and destination rectangles are halved until
they are less than 64K. The problem is that if GDI must continue to divide
the height by two (2) to get a buffer less than 64K, the source or
destination height could eventually reach one scan line. At this point, the
call fails because it cannot break up a scan line into subunits.
StretchBlt() and StretchDIBits() are not designed to provide unlimited stretching. However, they may fail a bit more prematurely than their design limitation.
RESOLUTION
If StretchBlt() or StretchDIBits() fails on a large stretch, an application can divide up the source bitmap, stretch the pieces individually, and position them correctly once stretched. Another alternative is to do a smaller stretch. There is no formula to determine exactly what bitmaps will fail at what stretch size.
STATUSMicrosoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article. MORE INFORMATION
To reproduce the problem, create a bitmap approximately 2048 pixels wide by
16 pixels high. Then, display the bitmap with the DIBVIEW sample from the
Windows 3.1 SDK. Choose Stretch To Window from DIBVIEW's Options menu, so
that the bitmap is stretched according to the size of the client window.
When the height is more than about 200 pixels, the bitmap will not be
displayed.
Modification Type: | Minor | Last Reviewed: | 3/7/2005 |
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Keywords: | kbbug kbpending KB111865 |
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