windows form Panel: drawtobitmap with larger size (resolution) c# output error

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Dear fellows, I have been searching for hours for this solution.
I successfully create jpeg file from panel with this code:

Bitmap panelImage = new Bitmap(mapPanel.Width, mapPanel.Height);

Graphics g = Graphics.FromImage((Image)panelImage);
g.InterpolationMode = InterpolationMode.HighQualityBicubic;

mapPanel.DrawToBitmap(panelImage, mapPanel.ClientRectangle);

g.DrawImage(panelImage, 0, 0, mapPanel.Width, mapPanel.Height);
g.Dispose();

panelImage.Save(saveImageDialog.FileName, ImageFormat.Jpeg);

the output is as below (the resolution is bad)

http://e1302.hizliresim.com/16/5/jtpjy.jpg

then I tried to make the resolution higer using this code:

Bitmap panelImage = new Bitmap(3508, 2480);
panelImage.SetResolution(300, 300);

Graphics g = Graphics.FromImage((Image)panelImage);
g.InterpolationMode = InterpolationMode.HighQualityBicubic;

mapPanel.DrawToBitmap(panelImage, mapPanel.ClientRectangle);

g.DrawImage(panelImage, 0, 0, 3508, 2480);
g.Dispose();

panelImage.Save(saveImageDialog.FileName, ImageFormat.Jpeg);

but it resulted like this:
http://e1302.hizliresim.com/16/5/jtny7.jpg

the panel area did not fill the whole page.

please help me

thank you

Posted 5-Feb-13 10:41am

Ace Supriatna

Updated 5-Feb-13 10:53am

Richard C Bishop

v5

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-02-05T11:46:00

Bitmap.SetResolution does not increase resolution. This term is misleading. The change in this parameter does not change anything in the presentation of the bitmap, in its content. It only fills in metadata showing how many dots per inch does it have by default. In other words, it defines some default scaling of the image, which can be used, say, for printing. Please see:
Record User Activity[^].

You want to increase the size of the bitmap in pixels. You are not even trying to do it: your bitmap is 3508x2480, and then you try to draw it as 3508x2480. Nothing changes. But if you really up-scaled the image, the quality of the result could be very poor. Actually, you cannot effectively enlarge the image by a considerable factor with good quality. More exactly, there are some "intellectual" algorithms for doing such things, such as fractal compression (http://en.wikipedia.org/wiki/Fractal_compression[^]; yes, compression, in that sense, can help to enlarge images with better quality), but the results are still limited. And this is called "re-sampling".

Even though the size of the bitmap in pixels is often called "resolution" and is related to resolution, in fact, this stuff has nothing to do with "resolution". Resolution is the ability to resolve two separate features as separate in imagine. Let's say, if you have two closely located features of some object, and then make an image with certain lens and camera, these two features can look blurred together or distinct. Resolution is usually measured in lines per mm (or inch) and characterized the ability to reproduce some sample pattern, usually a periodic pattern of contrast straight lines…

—SA