Check-in [2136c425c2]

{"tip": {
	"545":{"url":"./tip/545.md","keywords":"Tk, image","created":"19-May-2019","state":"Draft","tk-branch":"tip-545-svg-options","tcl-version":"8.7","vote":"Pending","type":"Project","title":"# TIP 545: image photo SVG options: remove -unit and add target","author":["Harald Oehlmann <[email protected]>"],"is-jest":false},
	"544":{"url":"./tip/544.md","keywords":"Tcl","":"","state":"Draft","type":"Project","author":["Jan Nijtmans <[email protected]>","François Vogel <[email protected]>"],"created":"15-May-2019","title":"# TIP 544: Export TclGetIntForIndex()","post-history":"","tcl-version":"8.7","vote":"Pending","tcl-branch":"tip-544","discussions-to":"Tcl Core list","is-jest":false},
	"543":{"url":"./tip/543.md","keywords":"Tcl, traces","created":"10-May-2019","post-history":"","state":"Draft","vote":"Pending","tcl-version":"9.0","type":"Project","title":"# TIP 543: Eliminate TCL\\_INTERP\\_DESTROYED flag value","author":["Don Porter <[email protected]>"],"is-jest":false},
	"542":{"url":"./tip/542.md","keywords":"Tcl","created":"10-May-2019","post-history":"","state":"Draft","tcl-branch":"utf-max","tcl-version":"8.7","vote":"Pending","type":"Project","title":"# TIP 542: New encodings: UTF-16, UCS-2, Support for switchable (Androwish-compatible) Full Unicode support.","discussions-to":"Tcl Core list","author":["Jan Nijtmans <[email protected]>","Jan Nijtmans <[email protected]>"],"is-jest":false},
	"541":{"url":"./tip/541.md","keywords":"Tcl","created":"8-May-2019","post-history":"","state":"Draft","tcl-branch":"bug-2858503fff","tcl-version":"8.6","vote":"In progress","type":"Project","title":"# TIP 541: Add support for 'end' index in ttk::combobox current","author":["François Vogel <[email protected]>"],"is-jest":false},
	"540":{"url":"./tip/540.md","keywords":"Tcl, Unix, pipeline","created":"03-May-2019","post-history":"","state":"Draft","vote":"Pending","tcl-version":"8.7","type":"Project","title":"# TIP 540: Add -signal Channel Configure Option to POSIX Pipes","author":["Donal K. Fellows <[email protected]>"],"is-jest":false},
	"539":{"url":"./tip/539.md","tcl-ticket":"2370575","keywords":"Tcl, dict filter, set intersection","created":"27-Nov-2008","obsoleted-by":"341","post-history":"","state":"Withdrawn","tcl-version":"8.7","vote":"Pending","type":"Project","title":"# TIP 539: Multiple dict filter patterns","author":["Lars Hellström <[email protected]>"],"is-jest":false},
	"538":{"url":"./tip/538.md","keywords":"Tcl","created":"9-April-2019","post-history":"","state":"Draft","tcl-branch":"digit-bit-60","tcl-version":"8.7","vote":"Pending","type":"Project","title":"# TIP 538: Externalize libtommath","author":["Jan Nijtmans <[email protected]>"],"is-jest":false},

	"5":{"url":"./tip/5.md","created":"17-Oct-2000","post-history":"","state":"Final","vote":"Done","tcl-version":"8.4","type":"Project","title":"# TIP 5: Make TkClassProcs and TkSetClassProcs Public and Extensible","author":["Eric Melski <[email protected]>"],"is-jest":false},
	"4":{"url":"./tip/4.md","created":"26-Oct-2000","post-history":"","state":"Draft","vote":"Pending","type":"Informative","title":"# TIP 4: Tcl Release and Distribution Philosophy","discussions-to":"news:comp.lang.tcl","author":["Brent Welch <[email protected]>","Donal K. Fellows <[email protected]>","Larry W. Virden <[email protected]>","Larry W. Virden <[email protected]>"],"is-jest":false},
	"3":{"url":"./tip/3.md","created":"14-Sep-2000","post-history":"","state":"Accepted","vote":"Done","type":"Process","title":"# TIP 3: TIP Format","author":["Andreas Kupries <[email protected]>","Donal K. Fellows <[email protected]>"],"is-jest":false},
	"2":{"url":"./tip/2.md","created":"12-Sep-2000","post-history":"","state":"Draft","vote":"Pending","type":"Process","title":"# TIP 2: TIP Guidelines","author":["Andreas Kupries <[email protected]>","Donal K. Fellows <[email protected]>","Don Porter <[email protected]>","Mo DeJong <[email protected]>","Larry W. Virden <[email protected]>","Kevin Kenny <[email protected]>"],"is-jest":false},
	"1":{"url":"./tip/1.md","created":"14-Sep-2000","obsoleted-by":"386","post-history":"","state":"Withdrawn","vote":"No voting","type":"Informational","title":"# TIP 1: TIP Index","author":["TIP Editor <[email protected]>"],"is-jest":false},
	"0":{"url":"./tip/0.md","created":"11-Dec-2000","post-history":"","state":"Final","vote":"Done","type":"Process","title":"# TIP 0: Tcl Core Team Basic Rules","author":["John Ousterhout <[email protected]>"],"is-jest":false},
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	"@max": 545
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<th>Type</th>
<th>Tcl Version</th>
<th>Status</th>
<th>Title</th>
<th>Impl.</th>
</tr></thead><tbody>

<tr class='state-draft type-project version-87'>
<td valign='top'><a href='./tip/545.md'>545</a></td>
<td valign='top'>Project</td>
<td valign='top'>8.7</td>
<td valign='top'>Draft</td>
<td valign='top' ><a href='./tip/545.md'>image photo SVG options: remove -unit and add target</a></td>
<td valign='top'><a href='/tk/timeline?r=tip-545-svg-options'>Link</a></td>
</tr>
<tr class='state-draft type-project version-87'>
<td valign='top'><a href='./tip/544.md'>544</a></td>
<td valign='top'>Project</td>
<td valign='top'>8.7</td>
<td valign='top'>Draft</td>
<td valign='top' ><a href='./tip/544.md'>Export TclGetIntForIndex()</a></td>
<td valign='top'><a href='/tcl/timeline?r=tip-544'>Link</a></td>

# TIP 545: image photo SVG options: remove -unit and add target 
	Author:         Harald Oehlmann <[email protected]>
	State:          Draft
	Type:           Project
	Vote:           Pending
	Created:        19-May-2019
	Keywords:       Tk, image
	Tcl-Version:    8.7
	Tk-Branch:     tip-545-svg-options
-----

# Abstract

Image photo SVG support was added to Tk by TIP 507.
This TIP is about the options of SVG rendering:

   *   The option "-unit" has no effect, as it sets the unit of the intermediate representation.
   *   The option "-scale float" is the essential tool to set rendering scaling. Nevertheless, to scale to a given height or width, a two-step procedure is required. This common case should be implemented by a one step procedure.

# Rationale

This TIP included two components:

## Remove option "-unit"

Remove the option "-unit", which has no effect.
The given unit is used to set the unit of the intermediate set of polygons.
The final unit is pixel anyway, so setting this to anything else than pixels does not make sense.

## Add a possibility to scale to a given width or height in pixels

A common usage of svg is to render button images for a given button height or width.
Buttons of applications may have all the same height or width when aranged in button lines aranged horizontally or vertically.

The current solution to render a svg to a given height "$height" is:

    image create photo p -file "test.svg"
    set imageHeight [image height p]
    p configure [list svg -scale [expr {double($height) / $imageHeight}]

This two step procedure has a high performance impact, as the image is rendered twice.
The aim is to render it only once by one parameter.

# Specification

## Remove option "-unit"

## Add new option -scaletoheight

The option "-scaletoheight entier" specifies the image height in pixels to scale to.
The image width is found by the aspect-ratio.

Example with an image "test.svg" with an aspect ration of width:height = 2:1.
The required height is 16 pixels:

    % image create photo p -file "test.svg" -format {svg -scaletoheight 16}
    p
    % image height p
    16
    % image width p
    32

The entier argument must be positive.
The option may not be specified together with "-scale" and/or "-scaletowidth".

## Add new option -scaletowidth

The option "-scaletowidth entier" specifies the image width in pixels to scale to.
The image height is found by the aspect-ratio.

Example with an image "test.svg" with an aspect ration of width:height = 2:1.
The required width is 16 pixels:

    % image create photo p -file "test.svg" -format {svg -scaletowidth 16}
    p
    % image width p
    16
    % image height p
    8

The entier argument must be positive.
The option may not be specified together with "-scale" and/or "-scaletoheight".

# Implementation

Implementation may start soon with the tag tip-545-svg-options.

# Copyright

This document has been placed in the public domain.