iText gradient issue in landscape - itext

Question

Having used gradients in iText in the past with no problems, suddenly i have an issue with it not working and narrowed it down to the fact that
this time i am working in landscape, (technically PageSize.A4.rotate()). The rotate() makes something happen that prevents the gradient from working as expected (by me).
To illustrate, i've adapted the example of the pink-blue triangle http://developers.itextpdf.com/question/how-add-shading-pattern-custom-shape
public class GradientProblem {
public static void main(String[] args) throws FileNotFoundException, DocumentException {
Document doc = new Document(PageSize.A4);
PdfWriter writer = PdfWriter.getInstance(doc, new FileOutputStream(new File("gradientProblem.pdf")));
doc.open();
drawSexyTriangle(writer);
doc.setPageSize(PageSize.A4.rotate());
doc.newPage();
drawSexyTriangle(writer);
doc.close();
}
private static void drawSexyTriangle(PdfWriter writer) {
PdfContentByte canvas = writer.getDirectContent();
float x = 36;
float y = 400;
float side = 70;
PdfShading axial = PdfShading.simpleAxial(writer, x, y, x + side, y, BaseColor.PINK, BaseColor.BLUE);
PdfShadingPattern shading = new PdfShadingPattern(axial);
canvas.setShadingFill(shading);
canvas.moveTo(x,y);
canvas.lineTo(x + side, y);
canvas.lineTo(x + (side / 2), (float)(y + (side * Math.sin(Math.PI / 3))));
canvas.closePathFillStroke();
}
}
Notice that the shading of the triangle on the first page is pink-blue, but on the second rotated page is just blue.
is this a bug, or expected behaviour?
if expected, how does the co-ordinate system work, ie what do the x0, y0, x1, y1 parameters to simpleAxial really mean?
The obvious work-around is to construct the appropriate page-size without rotation.
However using rotate() appears to be the advised approach, and when i have gradient code deep inside a re-useable table or cell event i can't really know how the page was constructed (or can i, i just don't know how?)
Any tips or insight would be much appreciated.
PS: tried iText 5.5.8 and 5.5.9

Answer 1

The problem is that while itext content adding functionalities do take the page rotation into account (they translate the given coordinates so that in the rotated page x goes right and y goes up and the origin is in the lower left), the shading pattern definitions (which are not part of the page content but externally defined) don't.
Thus, you have to make the shading definition rotation aware, e.g. like this:
Document doc = new Document(PageSize.A4);
PdfWriter writer = PdfWriter.getInstance(doc, new FileOutputStream(new File(RESULT_FOLDER, "gradientProblem.pdf")));
doc.open();
drawSexyTriangle(writer, false);
doc.setPageSize(PageSize.A4.rotate());
doc.newPage();
drawSexyTriangle(writer, true);
doc.close();
with
private static void drawSexyTriangle(PdfWriter writer, boolean rotated)
{
PdfContentByte canvas = writer.getDirectContent();
float x = 36;
float y = 400;
float side = 70;
PdfShading axial = rotated ?
PdfShading.simpleAxial(writer, PageSize.A4.getRight() - y, x, PageSize.A4.getRight() - y, x + side, BaseColor.PINK, BaseColor.BLUE)
: PdfShading.simpleAxial(writer, x, y, x + side, y, BaseColor.PINK, BaseColor.BLUE);
PdfShadingPattern shading = new PdfShadingPattern(axial);
canvas.setShadingFill(shading);
canvas.moveTo(x,y);
canvas.lineTo(x + side, y);
canvas.lineTo(x + (side / 2), (float)(y + (side * Math.sin(Math.PI / 3))));
canvas.closePathFillStroke();
}
(DrawGradient.java)