I cut some code but this is basically how I rotate a bitmap.

Can't be the best way because it takes too long!

Any help would be appreciated.



'Rotate180

Dim TmpBitmap As New Drawing.Bitmap(OldWidth, OldHeight)

For X As Integer = 0 To OldWidth - 1

For Y As Integer = 0 To OldHeight - 1

TmpBitmap.SetPixel(OldWidth - X - 1, OldHeight - Y - 1,
CType(PictureBoxPic.Image, Drawing.Bitmap).GetPixel(X, Y))

Next Y

Next X

PictureBoxPic.Image.Dispose()

PictureBoxPic.Image = TmpBitmap

End Sub

" active" <activeNOSPAM (AT) a-znet (DOT) com> wrote

SetPixel and GetPixel are slow. There are a few ways to do this, the last is
likely the best:
1) Have a look into lockbits
2) Use a graphics object to paint the bitmap onto itself (or a temp bitmap
if that causes problems)
3) Use Bitmap.Rotate

Seeing no 3 is a single line of code that does everything you want I'd
suggest that would be the best option :-)

Michael

You are so going to kick yourself...

RotateFlip

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" active" <activeNOSPAM (AT) a-znet (DOT) com> wrote

I signed on early today hoping to beat any replies. I did find that Image
can rotate and flip itself late yesterday and tried it.

But I have another application in which the amount of rotation is arbitrary.
So I looked up LockBits after I read your replies and am not sure from the
example how to apply it in this situation. I'll read somemore later but if
you happen to know of an example similar to my app it would help.

Anyway, I wanted to reply now so I can say thanks for the replies.

Thanks

" active" <activeNOSPAM (AT) a-znet (DOT) com> wrote

Look into no 2 in my post. You need to create a graphics object and paint
the bitmap onto itself. You can use graphics.RotateTransform to rotate the
way in which it paints the bitmap onto itself. Now I'm not sure if you can
paint a bitmap onto itself, if you can't then you should create a copy.

Michael

I have to admit I passed over item 2 because I couldn't understand how
coping would do it, but I see now.

Thanks

"Michael C" <nospam (AT) nospam (DOT) com> wrote

You cannot copy a bitmap onto itself.

--
--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

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"Michael C" <nospam (AT) nospam (DOT) com> wrote

Try something like this..


Bitmap bm=(Bitmap)Image.FromFile("the image");
Bitmap copy=new Bitmap(bm.Width, bm.Height);
Graphics g=Graphics.FromImage(copy);
Matrix mx=new Matrix();
Matrix.RotateAt(bm.Width/2,bm.Height/2);
g.DrawImage(bm);
copy.Save("file.xxx",ImageFormat.jpg);

--
--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

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" active" <activeNOSPAM (AT) a-znet (DOT) com> wrote

I can verify that.
I tried


"Bob Powell [MVP]" <bob (AT) spamkillerbobpowell (DOT) net> wrote

I gave it a quick try earlier and it evidently rotated around something
other than the center of the image.

I suspect your code fixes that.

thanks
"Bob Powell [MVP]" <bob (AT) spamkillerbobpowell (DOT) net> wrote