Apache PDFBox Renders Straight Line Crooked in PNG

问题

I have a PDF that when I render it to a png it renders a line crooked, or rather with a step in it. This is the PDF and what it should look like: https://drive.google.com/file/d/1E-zucbreD7pVwWc3Z4MNe_lzsP6D9m49/view

Here is the full PNG rendering using PDFBox 2.0.13 and openjdk version 1.8.0_181:

And here is the specific portion of the PNG that has the step:

回答1:

Excerpt of the page content stream:

q
1 0 0 1 35.761 450.003 cm
0 i
0.75 w
0 0 m
50.923 0 l
S
Q

q
1 0 0 1 86.139 450 cm
0 i
0.75 w
0 0 m
14.9 0 l
S
Q

("cm" is an affine transform, "m" a moveto, "l" a lineto). One can see that the two lines are slightly different, one at 450.003, the other one at 450.

Here's some code that simulates the error by replicating what PDFBox is doing:

BufferedImage bim = new BufferedImage(612, 792, BufferedImage.TYPE_INT_ARGB);
Graphics2D g = (Graphics2D) bim.getGraphics();
RenderingHints r = new RenderingHints(null);
r.put(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
r.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
r.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g.addRenderingHints(r);
g.translate(0, 792);
g.scale(1, -1);
g.setStroke(new BasicStroke(0.75f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_MITER, 10));
g.setColor(Color.black);
GeneralPath path = new GeneralPath();
path.moveTo(35.761f, 450.003f);
path.lineTo(35.761f + 50.923f, 450.003f);
g.draw(path);
path = new GeneralPath();
path.moveTo(86.139f, 450f);
path.lineTo(86.139f + 14.9f, 450f);
g.draw(path);
g.dispose();
ImageIO.write(bim, "png", new File("...."));

One can get rid of the error by commenting this line:

r.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

This could be done in the source code of PDFBox, or by passing the renderingHints in PDFRenderer.setRenderingHints(). However that one isn't available now, but will be available in 2.0.14 (see issue PDFBOX-4435, try a snapshot). And you can expect the rendering to be of poor quality by not having anti aliasing.

Update: instead of removing the line mentioned above, add this one:

r.put(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

Source.

来源：https://stackoverflow.com/questions/54658008/apache-pdfbox-renders-straight-line-crooked-in-png

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