Changes between Version 13 and Version 14 of MapGuideRfc60


Ignore:
Timestamp:
Jan 8, 2010 1:09:08 PM (9 years ago)
Author:
waltweltonlair
Comment:

Mark implementation as completed, and fix some minor formatting issues.

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  • MapGuideRfc60

    v13 v14  
    77== Status ==
    88
    9 ||RFC Template Version||(1.0)||
    10 ||Submission Date||(27.02.2009)||
    11 ||Last Modified||(UV Wildner) [[Timestamp]]||
    12 ||Author||(UV Wildner)||
    13 ||RFC Status||(adopted)||
    14 ||Implementation Status||(in testing)||
    15 ||Proposed Milestone||(2.1)||
     9||RFC Template Version||1.0||
     10||Submission Date||27.02.2009||
     11||Last Modified||UV Wildner [[Timestamp]]||
     12||Author||UV Wildner||
     13||RFC Status||adopted||
     14||Implementation Status||completed||
     15||Proposed Milestone||2.1||
    1616||Assigned PSC guide(s)||Bruce Dechant||
    1717||'''Voting History'''||May 7, 2009||
     
    2424== Overview ==
    2525
    26 The color quantization for PNG8 tiles does not preserve the base colors of the map. This leads to visible color differences in adjacent map tiles.
    27 By providing the base colors of the map as a palette to the image renderer the visual appearance of the map can be significantly improved.
     26The color quantization for PNG8 tiles does not preserve the base colors of the map. This leads to visible color differences in adjacent map tiles. By providing the base colors of the map as a palette to the image renderer the visual appearance of the map can be significantly improved.
    2827
    2928== Motivation ==
    3029
    31 The color palette for PNG8 tiles is computed in the AGG renderer from truecolor tiles (AGGImageIO.cpp) on a one by one basis.
    32 The used quantization algorithm in the gd library (gd_topal.c) does not preserve the base colors of the map as they are not know at this place.
    33 Therefore adjacent map tiles might use different colors for map areas crossing tile boundaries. This is very obvious and disturbing to the human eye.
     30The color palette for PNG8 tiles is computed in the AGG renderer from truecolor tiles (AGGImageIO.cpp) on a one by one basis. The used quantization algorithm in the gd library (gd_topal.c) does not preserve the base colors of the map as they are not know at this place. Therefore adjacent map tiles might use different colors for map areas crossing tile boundaries. This is very obvious and disturbing to the human eye.
    3431
    3532Ticket #813 PNG8 Compression isn't preserving fill colors
     
    3734== Proposed Solution ==
    3835
    39 By providing the base colors of the map in a palette file and using an improved color quantification algorithm which adds a forced palette to the image the resulting map can be significantly improved.
    40 This can be done by using the median-cut algorithm as used in the mapserver code base in the function `ImageCopyForcePaletteGD`.
     36By providing the base colors of the map in a palette file and using an improved color quantification algorithm which adds a forced palette to the image the resulting map can be significantly improved. This can be done by using the median-cut algorithm as used in the mapserver code base in the function `ImageCopyForcePaletteGD`.
    4137
    4238{{{
     
    5753}}}
    5854
    59 == server code integration ==
     55== Server Code Integration ==
    6056
    61 The interesting task is how to feed the base colors of the map to the Image Renderer making the image.
    62 The base colors of a map can be extracted most efficiently during map generation in MapingUtil::StylizeLayers().
    63 To do this the VectorScaleRange gets an additional method called VectorScaleRange::GetUsedColorList().
     57The interesting task is how to feed the base colors of the map to the Image Renderer making the image. The base colors of a map can be extracted most efficiently during map generation in MappingUtil::!StylizeLayers().
     58To do this the !VectorScaleRange gets an additional method called VectorScaleRange::!GetUsedColorList().
    6459This is a computed property implemented as a singleton which creates the list upon access. Subsequent requests from other threads read the same list. The singleton is not protected with a mutex as a second thread would recreate the same datastructure....in the worst case I can imagine a few kBytes of memory leak with a very low probability.... less costly than a mutex I suppose.
    6560
    66 At the end of the stylization GetUsedColorList is called and the resulting color list is stored in the runtime map object MgMap.
    67 (Map->SetColorPalette(pStringColorList)) This method sorts and uniquifies the color list upon storage.
     61At the end of the stylization !GetUsedColorList is called and the resulting color list is stored in the runtime map object !MgMap (Map->!SetColorPalette(pStringColorList)). This method sorts and uniquifies the color list upon storage.
    6862
    69 The colors from the MdfMModel are MdfStrings and the algorithm simply collects all different strings. So in order to support expressions for those colors the list simply needs to be interpreted when read from the MgMap object.
     63The colors from the !MdfModel are !MdfStrings and the algorithm simply collects all different strings. So in order to support expressions for those colors the list simply needs to be interpreted when read from the !MgMap object.
    7064
    71 The RenderingService reads the color list from the map object, and converts it into a list of RsColor objects.
    72 This color palette is then passed down via the AGGRenderer to the AGGImageIO objects Save method. Here the png color quantification
    73 algorithm is included to force the provided palette into the rendered image - this way making sure that the correct base colors survive the compression and/or color quantization.
    74 see also the sequence [http://trac.osgeo.org/mapguide/attachment/wiki/MapGuideRfc60/GetTile2.png]
     65The !RenderingService reads the color list from the map object, and converts it into a list of !RS_Color objects.
     66This color palette is then passed down via the AGGRenderer to the AGGImageIO object's Save method. Here the png color quantification algorithm is included to force the provided palette into the rendered image - this way making sure that the correct base colors survive the compression and/or color quantization.  See also the sequence [http://trac.osgeo.org/mapguide/attachment/wiki/MapGuideRfc60/GetTile2.png]
    7567
    7668== Implications ==
    7769
    78 No Implications are intended as this behaviour is desired by default. We just get better looking maps. The cost of extracting the colors from the in-memory representation of the XML data describing the map are presumed to be negligable. However, the color quantification is a bit more costly.
     70No Implications are intended as this behaviour is desired by default. We just get better looking maps. The cost of extracting the colors from the in-memory representation of the XML data describing the map are presumed to be negligible. However, the color quantification is a bit more costly.
    7971
    8072== Test Plan ==
     
    8476setting up a unit test seems excessively complex. Any ideas are most welcome.
    8577
    86 So far some debugging code has been included to verify the collection of the colors within the rendering service.
    87 The success is then evaluated on visually inspecting the map and testing if the base colors made it through using IrfanView.
     78So far some debugging code has been included to verify the collection of the colors within the rendering service. The success is then evaluated on visually inspecting the map and testing if the base colors made it through using !IrfanView.
    8879
    8980Any suggestions are most welcome.
     
    9384Some funding is to be provided by Explore Australia.
    9485
    95 == closed Issues ==
     86== Closed Issues ==
    9687
    97 1. No user stored palettes are used in this approach as the colors are defined in the map & layer definitions. The whole idea of providing the colors in an external file has been dropped as its more consistent and also fairly easy to create another version of the map having  other colors defined within.
    98 Supplying an user specified color palette to override the colors specified in the map fails at the missing mapping from a linear color list to the complex hierarchical structure of the map definition.
     881. No user stored palettes are used in this approach as the colors are defined in the map and layer definitions. The whole idea of providing the colors in an external file has been dropped as it's more consistent and also fairly easy to create another version of the map having other colors defined within. Supplying a user specified color palette to override the colors specified in the map fails at the missing mapping from a linear color list to the complex hierarchical structure of the map definition.
    9989
    100 2. The quantization algorithm can use quite some memory. 3 different memory allocation schemes have been provided. [[BR]]
    101 Due to recent problems in low memory situations a choice has been made to use the most memory conservative stack based allocation scheme.
     902. The quantization algorithm can use quite some memory. Three different memory allocation schemes have been provided. Due to recent problems in low memory situations a choice has been made to use the most memory conservative stack based allocation scheme.
    10291
    103 3. In this phase only the colors from the VectorLayerDefinitions and in there the Area, Line, and Point Symbolizations are parsed
    104 as cleartext. Any further evaluation requires resource lookups which are a higher order of complexity and should not be permanently enabled.
     923. In this phase only the colors from the !VectorLayerDefinitions and in there the Area, Line, and Point Symbolizations are parsed as cleartext. Any further evaluation requires resource lookups which are a higher order of complexity and should not be permanently enabled.
    10593
    106 4. No more memory issues. After some problems the code has been changed to duplicate any data from the MdfModel. Now the objects are created after stylization and destroyed after the tile has been created.
     944. No more memory issues. After some problems the code has been changed to duplicate any data from the !MdfModel. Now the objects are created after stylization and destroyed after the tile has been created.
    10795
    108 5. The algorithm parsing the MdfModel collects all different MdfStrings from the color fields. In order to support expressions for those colors the list simply needs to be reinterpreted when read from the MgMap object. Like the resource lookup this can be added at a later point in time when test cases and clearer specs have been established.
     965. The algorithm parsing the !MdfModel collects all different !MdfStrings from the color fields. In order to support expressions for those colors the list simply needs to be reinterpreted when read from the !MgMap object. Like the resource lookup this can be added at a later point in time when test cases and clearer specs have been established.