英文:
Converting between pixels and graphviz sizes/coordinates
问题
我如何将PNG渲染的图形的坐标转换为从-Tjson或-Tjson0获得的坐标？例如，我有一个大小为167 x 251的PNG，但.json文件中的边界框（bb）为117 x 180。我需要能够显示一个图形，在图形上的某处单击，然后让Python响应所单击的节点，但我无法弄清楚这个转换。
英文:
How can I translate the coordinates of a PNG render of a graph, to the coordinates I get from -Tjson or -Tjson0? For example, I have a PNG that's 167 x 251, but the .json file says the bounding box (bb) is 117 x 180. I need to be able to display a graph, click somewhere on the graph, and have Python respond with the node clicked, but I can't figure out this conversion.
答案1
得分: 1
Graphviz使用“points”（pts）作为位置和bb值的单位（在此页面的某个地方 - https://graphviz.org/doc/info/attrs.html - 您会找到此信息：目前，大多数设备无关的单位要么是英寸，要么是点，我们将其视为每英寸72点。）
此外，默认的输出设置为96 dpi（https://graphviz.org/docs/attrs/dpi/）
因此，bb尺寸/72应该等于png尺寸/96。
几乎，但不完全相等！
猜测最后需要匹配这两组尺寸的部分是考虑pad（https://graphviz.org/docs/attrs/pad/）。将4点（4/72英寸）添加到每个Graphviz pos值中，将8点（8/72）添加到bb总宽度和高度中。
英文:
Graphviz uses "points" (pts) - 72/inch as the unit for pos and bb values (somewhere on this page -https://graphviz.org/doc/info/attrs.html- you will find this:
At present, most device-independent units are either inches or points, which we take as 72 points per inch.)
Furthermore the default for output is set to 96 dpi (https://graphviz.org/docs/attrs/dpi/)
So bb dimensions /72 should equal png dimensions /96.
Almost, but not quite!
As a guess, the last bit needed to match the two sets of dimensions, is to factor in pad (https://graphviz.org/docs/attrs/pad/). Add 4 points (4/72 inches) to every Graphviz pos value and 8 points (8/72 to the bb total width & height)
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