MakeBitmap from the Diagram

800k? You said 26k before.
An 800k wide bitmap might take 6GB or so memory. Double that if you then need to convert it.
If this describes your situation, then memory exceptions could easily cause rendering problems.

Hi,
My mistake . 800 - 1800k it’s total size of the PNG.
Max wide of the diagram untill now it’s 29k +.
So i implemented your suggestion and after some loop unit tests fall in memory exceptions , despite of fact that i release all object .Net Garbage Collector manage big size object inside heap in the different way. Probability that prev. stick bitmap image in the memory very high.
Sometimes when i use this code:
//create a bitmap to hold the combined image
finalImage = new System.Drawing.Bitmap(width, height);
where width = 29500 i fall in exception Invalid value.
just after second attempt to export image