From 179fa413b047bede6e32109e2ce82437c5fb8d34 Mon Sep 17 00:00:00 2001 From: MenTaLguY Date: Mon, 16 Jan 2006 02:36:01 +0000 Subject: moving trunk for module inkscape (bzr r1) --- share/tutorials/tutorial-tracing.svg | 215 +++++++++++++++++++++++++++++++++++ 1 file changed, 215 insertions(+) create mode 100644 share/tutorials/tutorial-tracing.svg (limited to 'share/tutorials/tutorial-tracing.svg') diff --git a/share/tutorials/tutorial-tracing.svg b/share/tutorials/tutorial-tracing.svg new file mode 100644 index 000000000..4397e472e --- /dev/null +++ b/share/tutorials/tutorial-tracing.svg @@ -0,0 +1,215 @@ + + + + + + + + + + + + + + + + + image/svg+xml + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ::TRACING + + + + + + +One of the features in Inkscape is a tool for tracing a bitmap image +into a <path> element for your SVG drawing. These short notes +should help you become acquainted with how it works. + + + + +Currently Inkscape employs the Potrace bitmap tracing engine (potrace.sourceforge.net) by Peter Selinger. +In the future we expect to allow alternate tracing programs; for now, however, this fine +tool is more than sufficient for our needs. + + +Keep in mind that the Tracer's purpose is not to reproduce an exact duplicate of the +original image; nor is it intended to produce a final product. No autotracer can do +that. What is does is give you a set of curves which you can use as a resource for your +drawing. + + +Potrace interprets a black and white bitmap, and produces a set of curves. For Potrace, +we currently have three types of input filters, to convert from the raw image to +something that Potrace can use. + + +Generally the more dark pixels in the intermediate bitmap, the more tracing that Potrace +will perform. As the amount of tracing increases, more CPU time will be required, and +the <path> element will become much larger. It is suggested that the user experiment +with lighter intermediate images first, getting gradually darker to get the desired +proportion and complexity of the output path. + + +To use the tracer, load or import an image, select it, +and select the Path > Trace Bitmap item, or Shift+Alt+B. + + +main options within the trace dialog + +The user will see the three filter options available: + + + +Brightness Threshold + + + +This merely uses the sum of the red, green and blue (or shades of gray) of a pixel as an +indicator of whether it should be considered black or white. The threshold can be set +from 0.0 (black) to 1.0 (white). The higher the threshold setting, the fewer the number +pixels that will be considered to be \u201cwhite\u201d, and the intermediate image with +become darker. + + +Original ImageBrightness ThresholdFill, no StrokeBrightness ThresholdStroke, no Fill + + +Optimal Edge Detection + + + +This uses the edge detection algorithm devised by J. Canny, as a way of quickly finding +isoclines of similar contrast. This will produce an intermediate bitmap that will look +less like the original image than does the result of Brightness Threshold, but will +likely provide curve information that would otherwise be ignored. The threshold setting +here (0.0 \u2013 1.0) adjusts the brightness threshold of whether a pixel adjacent to a +contrast edge will be included in the output. This setting can adjust the darkness or +thickness of the edge in the output. + + +Original ImageEdge DetectedFill, no StrokeEdge DetectedStroke, no Fill + + +Color Quantization + + + +The result of this filter will produce an intermediate image that is very different from +the other two, but is very useful indeed. Instead of showing isoclines of brightness or +contrast, this will find edges where colors change, even at equal brightness and +contrast. The setting here, Number of Colors, decides how many output colors there +would be if the intermediate bitmap were in color. It then decides black/white on +whether the color has an even or odd index. + + +Original ImageQuantization (12 colors)Fill, no StrokeQuantization (12 colors)Stroke, no Fill + +The user should try all three filters, and observe the different types of output for +different types of input images. There will always be an image where one works better +than the others. + + +After tracing, it is also suggested that the user try Path > Simplify +(Ctrl+L) on the output path, to reduce the number of nodes. This can +make the output of Potrace much easier to edit. For example, here is a typical tracing +of the Old Man Playing Guitar: + + +Original ImageTraced Image / Output Path(1,551 nodes) + +Note the enormous number of nodes in the path. After hitting Ctrl+L, +this is a typical result: + + +Original ImageTraced Image / Output Path - Simplified(384 nodes) + +The representation is a bit more approximate and rough, but the drawing is much simpler +and easier to edit. Keep in mind, that what you want is not an exact rendering of the +image, but a set of curves that you can use in your drawing. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + image/svg+xml + + + + + + + + + + + + + + + + + + + + + + + + + + + + \ No newline at end of file -- cgit v1.2.3