Feature: post process tiles with ColorFiltered widget

[matthiasdittmer]

Hello, I suggest a small update to TileLayerOptions with an optional parameter for a ColorFilter.matrix to post process the tiles. Widget ColorFiltered.

Below the modified code sample for gray scale tiles (hard coded). Could also be used for visual enhancements (contrast, night vision, ...).

    return ColorFiltered(
        colorFilter: ColorFilter.matrix(<double>[
          0.2126,0.7152,0.0722,0,0,
          0.2126,0.7152,0.0722,0,0,
          0.2126,0.7152,0.0722,0,0,
          0,0,0,1,0,
        ]),
      child: Opacity(
        opacity: options.opacity,
        child: Container(
          color: options.backgroundColor,
          child: Stack(
          children: tileWidgets,
        ),
      ),
      ),
    );
  }

Edit: posted wrong code, now with child.

Not sure if this is the best place to do the filtering performance wise. Please comment.

[maRci002]

I checked it out and it looked awesome. However it should be the child of Opacity because if there are multiple Layers stacked on eachother this may cover lower layers or ColorFiltered will affect lower layers if opacity is low.

TileLayerOptions should have a final ColorFilter colorFilter; property and the final code would look like this in build method:

    var content = options.colorFilter == null
        ? Container(
            color: options.backgroundColor,
            child: Stack(
              children: tileWidgets,
            ),
          )
        : ColorFiltered(
            colorFilter: options.colorFilter,
            child: Container(
              color: options.backgroundColor,
              child: Stack(
                children: tileWidgets,
              ),
            ),
          );

    return Opacity(
      opacity: options.opacity,
      child: content,
    );

[matthiasdittmer]

Okay, I will open a PR.

[matthiasdittmer]

PR submitted. Closing this.