Merge sibling <g> nodes with identical attributes
In some cases, gnuplot generates a very suboptimal SVG content of the
following pattern:
<g color="black" fill="none" stroke="currentColor">
<path d="m82.5 323.3v-4.1" stroke="#000"/>
</g>
<g color="black" fill="none" stroke="currentColor">
<path d="m116.4 323.3v-4.1" stroke="#000"/>
</g>
... repeated 10+ more times here ...
<g color="black" fill="none" stroke="currentColor">
<path d="m65.4 72.8v250.5h420v-250.5h-420z" stroke="#000"/>
</g>
A more optimal pattern would be:
<g color="black" fill="none" stroke="#000">
<path d="m82.5 323.3v-4.1"/>
<path d="m116.4 323.3v-4.1"/>
... 10+ more paths here ...
<path d="m65.4 72.8v250.5h420v-250.5h-420z"/>
</g>
This patch enables that optimization by handling the merging of two
sibling <g> entries that have identical attributes. In the above
example that does not solve the rewrite from "currentColor" to "#000"
for the stroke attribute. However, the existing code already handles
that automatically after the <g> elements have been merged.
This change provides comparable results to --create-groups as shown by
the following diagram while being a distinct optimization:
+----------------------------+-------+--------+
| Test | Size | in % |
+----------------------------+-------+--------+
| baseline | 17961 | 100% |
| baseline + --create-groups | 17418 | 97.0% |
| patched | 16939 | 94.3% |
| patched + --create-groups | 16855 | 93.8% |
+----------------------------+-------+--------+
The image used in the size table above was generated based on the
instructions from https://bugs.debian.org/858039#10 with gnuplot 5.2
patchlevel 2. Beyond the test-based "--create-groups", the following
scour command-line parameters were used:
--enable-id-stripping --enable-comment-stripping \
--shorten-ids --indent=none
Note that the baseline was scour'ed repeatedly to stablize the image
size.
Signed-off-by: Niels Thykier <niels@thykier.net>
This commit is contained in:
Niels Thykier
parent
40753af88a
commit
cdf5e479a6
3 changed files with 115 additions and 0 deletions
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@ -1134,6 +1134,75 @@ def moveCommonAttributesToParentGroup(elem, referencedElements):
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return num
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def mergeSiblingGroupsWithCommonAttributes(elem):
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"""
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Merge two or more sibling <g> elements with the identical attributes.
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This function acts recursively on the given element.
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"""
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num = 0
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i = elem.childNodes.length - 1
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while i >= 0:
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currentNode = elem.childNodes.item(i)
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if currentNode.nodeType != Node.ELEMENT_NODE or currentNode.nodeName != 'g' or \
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currentNode.namespaceURI != NS['SVG']:
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i -= 1
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continue
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attributes = {a.nodeName: a.nodeValue for a in currentNode.attributes.values()}
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runStart, runEnd = i, i
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runElements = 1
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while runStart > 0:
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nextNode = elem.childNodes.item(runStart - 1)
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if nextNode.nodeType == Node.ELEMENT_NODE:
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if nextNode.nodeName != 'g' or nextNode.namespaceURI != NS['SVG']:
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break
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nextAttributes = {a.nodeName: a.nodeValue for a in nextNode.attributes.values()}
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hasNoMergeTags = (True for n in nextNode.childNodes
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if n.nodeType == Node.ELEMENT_NODE
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and n.nodeName in ('title', 'desc')
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and n.namespaceURI == NS['SVG'])
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if attributes != nextAttributes or any(hasNoMergeTags):
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break
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else:
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runElements += 1
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runStart -= 1
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else:
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runStart -= 1
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# Next loop will start from here
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i = runStart - 1
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if runElements < 2:
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continue
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# Find the <g> entry that starts the run (we might have run
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# past it into a text node or a comment node.
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while True:
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node = elem.childNodes.item(runStart)
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if node.nodeType == Node.ELEMENT_NODE and node.nodeName == 'g' and node.namespaceURI == NS['SVG']:
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break
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runStart += 1
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primaryGroup = elem.childNodes.item(runStart)
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runStart += 1
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nodes = elem.childNodes[runStart:runEnd+1]
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for node in nodes:
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if node.nodeType == Node.ELEMENT_NODE and node.nodeName == 'g' and node.namespaceURI == NS['SVG']:
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# Merge
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primaryGroup.childNodes.extend(node.childNodes)
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node.childNodes = []
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else:
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primaryGroup.childNodes.append(node)
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elem.childNodes.remove(node)
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# each child gets the same treatment, recursively
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for childNode in elem.childNodes:
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if childNode.nodeType == Node.ELEMENT_NODE:
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num += mergeSiblingGroupsWithCommonAttributes(childNode)
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return num
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def createGroupsForCommonAttributes(elem):
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"""
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Creates <g> elements to contain runs of 3 or more
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@ -3658,6 +3727,8 @@ def scourString(in_string, options=None):
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while removeDuplicateGradients(doc) > 0:
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pass
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if options.group_collapse:
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_num_elements_removed += mergeSiblingGroupsWithCommonAttributes(doc.documentElement)
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# create <g> elements if there are runs of elements with the same attributes.
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# this MUST be before moveCommonAttributesToParentGroup.
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if options.group_create:
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15
testscour.py
15
testscour.py
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@ -2075,6 +2075,21 @@ class MustKeepGInSwitch2(unittest.TestCase):
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'Erroneously removed a <g> in a <switch>')
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class GroupSiblingMerge(unittest.TestCase):
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def test_sibling_merge(self):
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doc = scourXmlFile('unittests/group-sibling-merge.svg',
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parse_args([]))
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self.assertEqual(doc.getElementsByTagName('g').length, 5,
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'Merged sibling <g> tags with similar values')
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def test_sibling_merge_disabled(self):
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doc = scourXmlFile('unittests/group-sibling-merge.svg',
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parse_args(['--disable-group-collapsing']))
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self.assertEqual(doc.getElementsByTagName('g').length, 8,
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'Sibling merging is disabled by --disable-group-collapsing')
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class GroupCreation(unittest.TestCase):
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def runTest(self):
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29
unittests/group-sibling-merge.svg
Normal file
29
unittests/group-sibling-merge.svg
Normal file
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@ -0,0 +1,29 @@
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<svg xmlns="http://www.w3.org/2000/svg">
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<desc>Produced by GNUPLOT 5.2 patchlevel 8</desc>
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<rect width="900" height="600" fill="none"/>
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<g color="black" fill="none">
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<path d="m88.5 564h9m777.5 0h-9" stroke="#000"/>
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<g transform="translate(80.2,567.9)" fill="#000" font-family="Arial" font-size="12" text-anchor="end">
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<text><tspan font-family="Arial">0</tspan></text>
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</g>
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</g>
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<g color="black" fill="none">
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<path d="m88.5 473h9m777.5 0h-9" stroke="#000"/>
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<g transform="translate(80.2,476.9)" fill="#000" font-family="Arial" font-size="12" text-anchor="end">
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<text><tspan font-family="Arial">5000</tspan></text>
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</g>
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</g>
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<g color="black" fill="none">
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<path d="m88.5 382h9m777.5 0h-9" stroke="#000"/>
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<g transform="translate(80.2,385.9)" fill="#000" font-family="Arial" font-size="12" text-anchor="end">
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<text><tspan font-family="Arial">10000</tspan></text>
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</g>
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</g>
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<g color="black" fill="none">
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<path d="m88.5 291h9m777.5 0h-9" stroke="#000"/>
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<g transform="translate(80.2,294.9)" fill="#000" font-family="Arial" font-size="12" text-anchor="end">
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<text><tspan font-family="Arial">15000</tspan></text>
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</g>
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</g>
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</svg>
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After Width: | Height: | Size: 1.1 KiB |
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