A few problems with SaveToBitmap (I am using GDI+ and saving to a .PNG file but all formats seem to have a limitation):

First, there seems to be an undefined limitation on the size of the file. I am trying to figure out how to calculate whether the file would be too large before saving. Any ideas what the exact limitation is?

What I am doing now is that if I see the file wasn't created properly, I adjust ImageExportOptions.ScaleFactor and keep reducing it until it works. Ugly, but at least it works.

And here is the where the crash comes in, when I try saving a huge picture (width=85000 pixels) which fails a few times until I get the ScaleFactor right, there is a huge peak in memory usage which results in app instability. When I try to do this a second time, my application crashes.

So:
1. How do I calculate the exact limitation/size so that I can set the ScaleFactor right?
2. You guys need to check for instability issues on save failure with huge pictures.

Quote:


We don't have any idea. As you can see in the SaveToBitmap help topic, that's a known problem. The CreateCompatibleBitmap function just returns a null value when called with dimensions and color depth that would require more than 10MB of memory, but we haven't found any reliable way to predict if that will happen (sometimes it works even with larger bitmaps).

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We do everything possible, which is to check for a NULL value in this case before trying to create a file. Indeed the memory peaks, but we can't call DeleteBitmap on the NULL value we receive from the create function.

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I don't see this happening in my test. The used memory stays at stable 20MB, and revert to 16MB after the loop completes (on a 1000x1000 bitmap):

For i = 1 To 100
	fcx.SaveToBitmap diag.fileName + Str(i), fcx.DocLeft, fcx.DocTop, fcx.DocRight, fcx.DocBottom
Next
 

As a solution, you might try exporting multiple bitmaps smaller than 10MB and glue them together using some image processing library. Another option is to export to WMF, which works fine even with huge flowcharts.

Hi,

From our experience, this limit is different on different systems, e.g. it works with 8000x8000 bitmaps on a test system of ours, but on most it fails around the 3000x3000 boundary (might be related to the size of some buffers in video drivers). I suppose you could count 8MB as the safe upper bound, and run the scaling code for larger bitmaps than that.

Stoyan