# Performance: see-through layers encode a PNG per tile

**URL:** <https://community.thinkgeo.com/t/performance-see-through-layers-encode-a-png-per-tile/12465>\
**Category:** WPF\
**Created:** [September 18, 2026, 12:16pm UTC](https://community.thinkgeo.com/t/performance-see-through-layers-encode-a-png-per-tile/12465 "2026-09-18T12:16:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Julian\_Thoms](https://community.thinkgeo.com/letter_avatar_proxy/v4/letter/j/b77776/32.png) [@Julian\_Thoms](https://community.thinkgeo.com/u/Julian_Thoms)\
**Post date:** [September 18, 2026, 12:16pm UTC](https://community.thinkgeo.com/t/performance-see-through-layers-encode-a-png-per-tile/12465/1 "2026-09-18T12:16:27Z")

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In ThinkGeo.Core 15.0.0-beta154, `Layer.DrawWithColorTransformation` (used for every layer with `Opacity < 1` ) renders the layer offscreen, applies the opacity into a new bitmap, and then calls `GetImageBytes()` followed by `new GeoImage(bytes)` . That is a full PNG encode and decode for every tile of every see-through layer, only to get a new image object.

Skia can draw the offscreen bitmap onto the tile with an alpha in one call ( `SKPaint` with an alpha colour), with no copy at all. Please replace the round trip with that.

Related: `GeoImage.Opacity` copies all pixels to managed memory and back. An `opacity` parameter on `GeoCanvas.DrawWorldImageWithoutScaling` / `DrawScreenImageWithoutScaling` would avoid that too.

Versions: ThinkGeo.Core / ThinkGeo.UI.Wpf 15.0.0-beta154, .NET 10, WPF.

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**Author:** ![Ben](https://community.thinkgeo.com/user_avatar/community.thinkgeo.com/ben/32/25720_2.png) [@Ben](https://community.thinkgeo.com/u/Ben)\
**Post date:** [September 19, 2026, 2:35am UTC](https://community.thinkgeo.com/t/performance-see-through-layers-encode-a-png-per-tile/12465/2 "2026-09-19T02:35:57Z")

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Hi Julian,

You were right, and it’s now fixed in 15.0.0-beta159, have a try.

Note: An opacity parameter on DrawWorldImageWithoutScaling / DrawScreenImageWithoutScaling: that would be a key API change and would affect user’s classes, (as we need to also change the corresponding virtual Core method), so we didn’t do it. It’s on the list though.

Thanks,  
Ben