PDFsharp - 绘制文本，围绕自定义 pivot 点旋转并移动它

Question

I would like to draw a text which is rotated around x degrees. Due to the fact I don't rotate it around it's center point I want to provide an offset too.

First I rotate the rectangle around the custom pivot point

graphics.RotateAtTransform(RotationInDegrees, pivotPoint);

and I know I can move the transform with

graphics.TranslateTransform(offsetX, offsetY);

but to calculate the offset I need to know the new directions, so top might be bottom now on 180 degrees.

I have a 2D vector representing a grid system where center is at (0|0), top left (-1|1), bottom right (1|-1) etc. So basically I could rotate first, then draw the text

textFormatter.DrawString(watermarkContent, Font, Brush, textBox, Format);

and after drawing the textBox I translate it. Then I could use this calculation to know the correct rotation

graphics.TranslateTransform(alignmentVector.X * -horizontalOffset, alignmentVector.Y * verticalOffset);

but this is not possible. I have to apply the transformations first and draw at the end. So how can I apply the horizontal and vertical offset to the rectangle correctly (by knowing the correct direction) after rotating?

Answer 1

The transformations apply to items that get drawn after setting the transformations. This allows to draw text at a 30° angle and other text at a 60° angle by changing the transformations later on.

So you have to apply the transformations before drawing the text. The transformation also applies to the "textbox" used to draw the text and there is no need to change that box.

Also see this sample:
http://www.pdfsharp.net/wiki/XForms-sample.ashx