Export diagram as bitmap

GoXam
1

Hello,

I have an implementation to export a diagram to a png file:

List existingParts = new List();

existingParts.AddRange(this.Diagram.Nodes);
existingParts.AddRange(this.Diagram.Links);

Rect bounds = this.Diagram.Panel.ComputeBounds(existingParts);

if (bounds != Rect.Empty)
{
bounds = DefaultLayoutFactory.SetDefaultExtraPageMargin(bounds);

double w = bounds.Width;
double h = bounds.Height;
double s = 1.0;

if (w > 65536)
{
s = 65536/ w;
}

if (h > 65536)
{
s = Math.Min(s, 65536/ h);
}

w = Math.Ceiling(ws);
h = Math.Ceiling(hs);

BitmapSource bmp = this.Diagram.Panel.MakeBitmap(new Size(w, h), 96, new Point(bounds.X, bounds.Y), s);
PngBitmapEncoder png = new PngBitmapEncoder();

png.Frames.Add(BitmapFrame.Create(bmp));

using (Stream stream = File.Create(filename))
{
png.Save(stream);
}
}
else
{
(new NoElementsFoundForExportMessage()).Submit();
}

If the diagram is very large (about height: 70000 and width: 90000) there I got a memory out of range exception. (BitmapSource bmp = this.Diagram.Panel.MakeBitmap…)

I know, that I shall reduce the 65536 “scale down” limit. I just play around with this value, because I want to avoid a reduction of bitmap export quality.

Is there any workaround, for example directly creating a PNG file (without bitmapsource) or rendering parts of the bitmap, encode it as png and stick these parts finaly together?

Kind regards,

Benedikt

2

PNG is a lossless compressed image format. Even though the result is a relatively small image file, the source needs to be an uncompressed bitmap of some sort. Chances are that the 65536x65536 pixel is at least 3 and probably 4 bytes per pixel means the image is 3GB or 4GB in memory.

As you suggest, you could render a bunch of more reasonably sized tiles as separate bitmaps and then separate PNG files. But whatever tool you use to stitch them together into a single image would have the same problem.