dotnet drawing api: imprecise Graphics.RotateTransform -- dotnet drawing api

imprecise Graphics.RotateTransform

thenext1
4/20/2007 12:12:03 PM

dotnet drawing api: I have an image representing a clock's minute hand and which I need to draw
in the 12 positions.
After fiddling a bit, i noticed that there's a strange offset from the hand
in one position (i.e. 3 PM) and the opposite (9 PM).
It seems that the RotateTransform function i'm using doesn't work correctly,
or alternatively that I can't manage to horizontally center the point of
rotation so that it rotates around an odd position.

To understand what I mean look here:
http://gemini.dynalias.net/web3/clock-net.png
The code I use for this drawing is the following:
float t = 0;
for (int i = 0; i < 12; i++)
{
e.Graphics.ResetTransform();
e.Graphics.TranslateTransform(100, 100);
e.Graphics.RotateTransform(i * 30);
e.Graphics.TranslateTransform(-3, -40);
e.Graphics.DrawImage(c.CetBitmap, 0, 0);
}
The png's width is 6 (hence, translated back 3 pixels)

Furthermore I tried doing the same thing with java's Graphics2d class, and
it works correctly: http://gemini.dynalias.net/web3/clock-java.png
The hand is perfectly aligned and coincident when in opposite positions.
The java code is:
AffineTransform base = g2d.getTransform();
for (int i = 0; i < 12; i++) {
g2d.setTransform(base);
g2d.translate(100,100);
g2d.rotate(i*Math.PI/6);
g2d.translate(-3, -40.0);
g2d.drawImage(NewJFrame.m, 0, 0, this);
}

Re: imprecise Graphics.RotateTransform

thenext1
4/21/2007 3:40:02 AM

Thanks... I've incidentally solved my problem setting the
Graphics.PixelOffsetMode to HighQuality....
I think .NET needs more documentation... (although it's already much better
than java, tho..)

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Re: imprecise Graphics.RotateTransform

Bob Powell [MVP]
4/21/2007 12:27:47 PM

All in the order...

e.Graphics.ResetTransform();
e.Graphics.TranslateTransform(-3, -40);
e.Graphics.RotateTransform(i * 30);
e.Graphics.TranslateTransform(100, 100);
e.Graphics.DrawImage(c.CetBitmap, 0, 0);

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

Ramuseco Limited .NET consulting
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