Hi,
Am 25.02.2014 00:32, schrieb John Hewson:
I’ve given the current implantation of tiling patterns an overhaul so that it
supports uncoloured tilings
and to simplify the existing code.
However, the scaling issues are not resolved. I’ve use the same approach to
scaling the pattern as
in Tilman’s patch, it is indeed correct to apply the CTM to the new page.
However, the issue with AWT
paint cannot be resolved. The issue is that AWT calls PaintContext#getRaster(x,
y, w, h) with the same
values irrespective of the DPI which we are rendering at. So, when we render a
page at 144dpi AWT is
asking its PaintContext to generate a raster at 72dpi and then it is upscaling
it to 144dpi, which causes
it to become pixelated.
To confirm that AWT is the problem I created custom PaintContext which returned
a raster with alternating
red and black 1px stripes. When rendering at 72dpi the stripes are 1px wide,
but when rendering at 144dpi
the stripes are 2px wide, meaning that the raster was upscaled by AWT after it
was rendered.
I'm not sure if AWT is the culprit here. I ran some tests a couple of days but
ran out of time, so that I couldn't get any reliable results. I suspect that we
don't apply the optional pattern matrix the correct way. But maybe that's just a
gut feeling which leads me into the wrong direction ....
-- John
BR
Andreas Lehmkühler
On 24 Feb 2014, at 13:54, Tilman Hausherr <[email protected]> wrote:
You have been using the version of the trunk, which has a scaling problem. If
you use my proposed patch it looks much better (see the images I attached). I
didn't check it in because Andreas had assigned the issue to himself. I might
do it after having updated my local version to the current trunk, unless there
is protest.
Tilman
Am 24.02.2014 20:45, schrieb John Hewson:
Hi All
There’s been lots of work recently on shading and tiling patterns and I’ve been
testing out some
of the new rendering capabilities. However, I think I’ve discovered a
fundamental problem with
using AWT’s PaintContext for drawing.
I noticed that the PDF from PDFBOX-1094 looks fine when rendered at the default
72dpi however
if I render it at 144dpi then the tiling patterns appear pixelated. As
expected, RenderUtil creates a
proportionally larger BufferedImage to render to and then calls
graphics#scale(x,y) so that everything
drawn to the graphics is scaled. This seems to work as expected for vectors and
drawImage, we get
nice crisp graphics at large scales. However, for our custom PaintContext
classes we get pixellated
graphics.
I decided to instrument the calls to ColoredTilingContext#getRaster(x, y, w, h)
at 72 and 144 dpi to see
if the problem is caused by up-scaling of paint *after* it is rendered to a
raster. This is indeed, the cause
and I observed the following calls for the PDFBOX-1094 file:
72 DPI
----------
x y w h
getRaster 302 586 76 76
getRaster 396 586 76 76
getRaster 344 662 86 86
getRaster 340 623 94 82
getRaster 302 317 76 76
getRaster 396 317 76 76
getRaster 344 393 86 87
getRaster 340 355 94 82
144 DPI
—————
x y w h
getRaster 302 586 76 76
getRaster 396 586 76 76
getRaster 344 662 86 86
getRaster 340 623 94 82
getRaster 302 317 76 76
getRaster 396 317 76 76
getRaster 344 393 86 87
getRaster 340 355 94 82
Perhaps there is some rendering hint or Graphics setting we’re not aware of? If
not we will have to migrate
away from using PaintContext and do the painting ourselves using a clipping
path. :-(
-- John
