Difference between revisions of "BlueprintRealUnit"
| Line 5: | Line 5: | ||
== The problem == | == The problem == | ||
=== Inkscape side === | === Inaccuracy === | ||
==== Inkscape side ==== | |||
Even if the user switch everywhere the unit to mm, inkscape | Even if the user switch everywhere the unit to mm, inkscape | ||
convert it to px unit and write it in the .svg file resulting inaccuracies. | convert it to px unit and write it in the .svg file resulting inaccuracies. | ||
=== SVG side === | ==== SVG side ==== | ||
All the units in svg drawing needs to be in px unit. | All the units in svg drawing needs to be in px unit. | ||
| Line 24: | Line 26: | ||
The correct solution would be to specify it in pixel and after tranform it. | The correct solution would be to specify it in pixel and after tranform it. | ||
=== Flipping the coordinate system === | |||
Ability to specify the origin of the coordinate system (top-left) vs. (bottom-left). | |||
== Use cases == | == Use cases == | ||
Revision as of 15:31, 6 June 2008
Summary
This blueprint tries to collect all information about how to implement real world units (in, mm) in a standard compliant way.
The problem
Inaccuracy
Inkscape side
Even if the user switch everywhere the unit to mm, inkscape convert it to px unit and write it in the .svg file resulting inaccuracies.
SVG side
All the units in svg drawing needs to be in px unit. The grammar in the SVG specification does not allow other units then pixel: http://www.w3.org/TR/SVG/paths.html#PathDataBNF
More information about coordinate system: http://www.w3.org/TR/SVG/coords.html
Examples: This is invalid in SVG:
<path d="M 0,0 L 30mm,0 L 30mm,30mm L 45mm,30mm" id="path7887" />
The correct solution would be to specify it in pixel and after tranform it.
Flipping the coordinate system
Ability to specify the origin of the coordinate system (top-left) vs. (bottom-left).
Use cases
1. Bob wants everything in mm
2. Bob wants everything in mm except fonts which he wants in points.
3. Bob wants mix units in mm and inch. But always want to see the original unit.
4. Bob does not care about units he wants just draw something to the web
More resource on the web
Related bug reports
#168753: SVG defaults to pixels (90dpi) despite default units Duplicates: #168516: Inkscape doesn't save page size units in plain svg #170738: preserve units
Viewbox related bug reports: #171203: Use viewBox to explicitly define a coordinate system
Related discussions in the past
On the inkscape-dev mailing list:
Although attaching parasite information to an svg element is not necessary, but maybe useful if additional information must be keeped about conversion inaccuracy. Please see this thread for more information: Attaching parasite information to an object (or group)