V0.8c -- Fixed #28

Hints for #27 added.
Added testdata files from issue#15

Author: Jürgen Weigert

centerline-trace.inx

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <inkscape-extension xmlns="http://www.inkscape.org/namespace/inkscape/extension">
-  <_name>Centerline Trace 0.8b</_name><!-- CAUTION: keep in sync with line 24 below and centerline_trace.py ca. line 55 __version__ = ... -->
-  <id>com.github.fablabnbg.inskscape-centerline-trace.dev</id>
+  <_name>Centerline Trace v0.8c</_name><!-- CAUTION: keep in sync with line 24 below and centerline_trace.py ca. line 55 __version__ = ... -->
+  <id>com.github.fablabnbg.inskscape-centerline-trace</id>
   <dependency type="extension">org.inkscape.output.svg.inkscape</dependency>
   <dependency type="executable" location="extensions">inkex.py</dependency>
   <dependency type="executable" location="extensions">centerline-trace.py</dependency>
@@ -24,13 +24,13 @@
   Autotrace options:
   </param>
   <param name="at-filter-iterations" type="int" min="0" max="20" _gui-text="--filter-iterations [0..20] (Default: 4)">4</param>
-  <param name="at-error-threshold" type="float" min="1.0" max="10.0" precision="1" _gui-text="--error-threshold [1.0..10.0] (Default: 2.0)">2.0</param>
+  <param name="at-error-threshold" type="float" min="1.0" max="5.0" precision="2" _gui-text="--error-threshold [1.0..5.0] (Default: 2.0)">2.0</param>
   <param name="about_who" type="description">(C) 2016-2018 Jürgen Weigert ([email protected]) and contributors.
   For updates, praise or bug reports please refer to
   https://github.com/fablabnbg/inkscape-centerline-trace
   </param>
   <!-- CAUTION: Keep in sync with line 3 above and with centerline_trace.py ca. line 61 __version__ = ... -->
-  <param name="about_version" type="description">Version 0.8b</param>
+  <param name="about_version" type="description">Version 0.8c</param>
 
   <effect needs-live-preview="false" >
     <object-type>path</object-type>

centerline-trace.py

@@ -56,11 +56,13 @@
 # 2018-08-31 jw, V0.8 -- MacOS instructions updated and MacOS path added for autotrace 0.40.0 from
 #                        https://github.com/jnweiger/autotrace/releases
 # 2018-09-01 jw, V0.8a -- Windows Path added
-# 2018-09-03 jw, V0.8b -- New option: cliprect, hairline, at_filter_iterations, at_error_threshold added. 
+# 2018-09-03 jw, V0.8b -- New option: cliprect, hairline, at_filter_iterations, at_error_threshold added.
 #                         Fixed stroke_width of scaled images.
+# 2018-09-04 jw, V0.8c -- Fixed https://github.com/fablabnbg/inkscape-centerline-trace/issues/28
+#                         Hints for https://github.com/fablabnbg/inkscape-centerline-trace/issues/27 added.
 
 
-__version__ = '0.8b'	# Keep in sync with centerline-trace.inx ca. line 3 and 24
+__version__ = '0.8c'	# Keep in sync with centerline-trace.inx ca. line 3 and 24
 __author__ = 'Juergen Weigert <[email protected]>'
 
 import sys, os, re, math, tempfile, subprocess, base64, time
@@ -75,8 +77,8 @@
   sys.exit(1)
 
 
-# debug = True
 debug = False
+# debug = True
 
 autotrace_exe = 'autotrace'
 
@@ -139,13 +141,14 @@ def __init__(self):
 
     p = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     return_code = p.wait()
-    f = p.stdout
-    err = p.stderr
 
-    out = p.communicate()[0]
+    out,err = p.communicate()
 
     found = out.find('AutoTrace')
     if found == -1:
+        print >>sys.stderr, err
+        if err.find('cannot open shared object file'):
+          print >>sys.stderr, "NOTE: This build of autotrace is incompatible with your system, try a different build.\n"
         print >>sys.stderr, "You need to install autotrace for this extension to work. Try https://github.com/jnweiger/autotrace/releases or search for autotrace version 0.40.0 or later."
         exit()
 
@@ -198,7 +201,7 @@ def svg_centerline_trace(self, image_file, cliprect=None):
     Then we run several iterations of autotrace and find the optimal black white threshold by evaluating
     all outputs. The output with the longest total path and the least path elements wins.
 
-    A cliprect dict with the keys x, y, w, h can be specified. All 4 are expected in the 
+    A cliprect dict with the keys x, y, w, h can be specified. All 4 are expected in the
     range 0..1 and are mapped to the image width and height.
     """
     num_attempts = self.candidates	# 15 is great. min 1, max 255, beware it gets much slower with more attempts.
@@ -252,7 +255,8 @@ def svg_centerline_trace(self, image_file, cliprect=None):
     if self.filter_median > 0:
       if self.filter_median % 2 == 0: self.filter_median = self.filter_median + 1	# need odd values.
       im = im.filter(ImageFilter.MedianFilter(size=self.filter_median))	                # feeble denoise attempt. FIXME: try ROF instead.
-    im = ImageOps.autocontrast(im, cutoff=2)	# linear expand histogram (an alternative to equalize)
+    im = ImageOps.autocontrast(im, cutoff=0)	# linear expand histogram (an alternative to equalize)
+    ## cutoff=2 destroys some images, see https://github.com/fablabnbg/inkscape-centerline-trace/issues/28
 
     # not needed here:
     # im = im.filter(ImageFilter.UnsharpMask(radius=2, percent=150, threshold=3))	# parameters depend on size of image!
@@ -324,7 +328,7 @@ def svg_pathstats(path_d):
       if debug: print >>self.tty, "bw from lut done: threshold=%d" % threshold
       if self.options.debug: bw.show(command="/usr/bin/display -title=bw:threshold=%d" % threshold)
       cand = { 'threshold':threshold, 'img_width':bw.size[0], 'img_height':bw.size[1], 'mean': ImageStat.Stat(im).mean[0] }
-      fp = tempfile.NamedTemporaryFile(prefix="certerlinetrace", suffix='.pbm', delete=False)
+      fp = tempfile.NamedTemporaryFile(prefix="centerlinetrace", suffix='.pbm', delete=False)
       fp.write("P4\n%d %d\n" % (bw.size[0], bw.size[1]))
       fp.write(bw.tobytes())
       fp.close()
@@ -347,6 +351,7 @@ def svg_pathstats(path_d):
         cand['svg'] = '<svg/>'                  # empty dummy
       else:
         os.unlink(fp.name)
+
       # <?xml version="1.0" standalone="yes"?>\n<svg width="86" height="83">\n<path style="stroke:#000000; fill:none;" d="M36 15C37.9219 18.1496 41.7926 19.6686 43.2585 23.1042C47.9556 34.1128 39.524 32.0995 35.179 37.6034C32.6296 40.8328 34 48.1105 34 52M36 17C32.075 22.4565 31.8375 30.074 35 36M74 42L46 38C45.9991 46.1415 46.7299 56.0825 45.6319 64C44.1349 74.7955 23.7094 77.5566 16.044 72.3966C7.27363 66.4928 8.04426 45.0047 16.2276 38.7384C20.6362 35.3626 27.7809 36.0006 33 36M44 37L45 37"/>\n</svg>
       try:
         xml = inkex.etree.fromstring(cand['svg'])
@@ -418,6 +423,7 @@ def effect(self):
     if self.options.hairline       is not None: self.hairline           = self.options.hairline
     if self.options.hairline_width is not None: self.hairline_width     = self.options.hairline_width
     # if self.options.debug          is not None: debug                   = self.options.debug
+    # self.options.debug = True
 
     self.calc_unit_factor()
 
@@ -465,12 +471,13 @@ def effect(self):
         cliprect['x'] = cliprect['x'] - svg_x_off
         cliprect['y'] = cliprect['y'] - svg_y_off
         cliprect['x'] = cliprect['x'] / svg_img_w
-        cliprect['y'] = cliprect['y'] / svg_img_h 
+        cliprect['y'] = cliprect['y'] / svg_img_h
         cliprect['w'] = cliprect['w'] / svg_img_w
-        cliprect['h'] = cliprect['h'] / svg_img_h 
+        cliprect['h'] = cliprect['h'] / svg_img_h
 
       # handle two cases. Embedded and linked images
       # <image .. xlink:href="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAT8AA ..." preserveAspectRatio="none" height="432" width="425" transform="matrix(1,0,-0.52013328,0.85408511,0,0)"/>
+      # <image .. xlink:href="xlink:href="data:image/jpeg;base64,/9j/4AAQSkZJRgAB..."
       # <image  .. xlink:href="file:///home/jw/schaf.png"
 
       href=str(node.get(inkex.addNS('href','xlink')))
@@ -496,12 +503,12 @@ def effect(self):
         type = href[11:11+l]			# 'png' 'jpeg'
         if debug: print >>self.tty, "embedded image: "+href[:11+l]
         img=base64.decodestring(href[11+l+8:])
-        f=tempfile.NamedTemporaryFile(mode="wb", suffix="."+type, delete=False)
+        f=tempfile.NamedTemporaryFile(mode="wb", prefix='centerlinetrace', suffix="."+type, delete=False)
         f.write(img)
         filename=f.name
         f.close()
       else:
-        inkex.errormsg(_("Neither file:// nor data:image/png; prefix. Cannot parse PNG image href "+href))
+        inkex.errormsg(_("Neither file:// nor data:image/; prefix. Cannot parse PNG/JPEG image href "+href[:200]+"..."))
         sys.exit(1)
       if debug: print >>self.tty, "filename="+filename
       #
@@ -540,7 +547,7 @@ def effect(self):
       ## insert the new path object
       inkex.etree.SubElement(self.current_layer, inkex.addNS('path', 'svg'), path_attr)
       ## delete the old image object
-      if self.replace_image: 
+      if self.replace_image:
         node.getparent().remove(node)
         if cliprect is not None:        # and its cliprect ...
           cliprect['node'].getparent().remove(cliprect['node'])