Concatenates the page's current transformation matrix and specified matrix.
ConcatMatrix(For example, if you want to rotate the coordinate system of the page by 45 degrees, use ConcatMatrix() as follows:
float rad1 = 45 / 180 * 3.141592;
myPage.ConcatMatrix (page, cos (rad1), sin (rad1), -sin (rad1), cos (rad1), 220, 350);
You will usually want to save the Graphics state first with the SaveState method and then restore the state with the RestoreState method.
Note this is advanced and powerful feature and we cannot support you much with it, refer to LibHaru documentation and examples if needing more info: https://github.com/libharu/libharu/wiki/API:-Graphics#HPDF_Page_Concat