* Implement gradient brush similar to PathGradientBrush (#969)
A gradient brush implementation that works similar to
System.Drawing.Drawing2D.PathGradientBrush.
This fixes#969, but only convex paths are supported for now.
* Update submodule to add test fixtures for #989
* Performance optimization
Use LengthSquared() instead of Length() when it's possible.
Avoid unnecessary ordering of elements.
* Avoid using LINQ in a hotspot
* Validate arguments for the public constructor
* Implement IDisposable and ensure inheritance calls base
* add ImageProcessingContextTests and move some other test classes
* loosen up tests and leave TODO notes
* No longer throws when DrawImage source does not overlap target
Previously, when DrawImage was used to overlay an image, in cases where the source image did not overlap the target image, a very confusing error was reported: "System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MaxDegreeOfParallelism"
Now, when this case happens, the DrawImage method will simply not affect the target image, which is the same way FillRegionProcessor handles such cases.
ParallelHelper.IterRows also now does more validation of the input rectangle so that any further cases of this kind of problem throw a more relvant exception. Note I switched from DebugGuard to Guard because IterRows is a public API and thus should always validate its inputs.
Fixes#875
* Refines DrawImage non-overlap error logic
Adresses PR feedback in #877.
Changes DrawImage shortcut to be less than or equal to. Also changes maxX calculation to use `Right` over `Width`. This is a semantic change that reflects intention better. No actual change because Top,Left for that rectanngle should always be 0,0.
And adds more informative argument names to ParallelHelper.IterRows error message.
* Non-overlapping DrawImage now throws
Adressing PR feedback from #877
DrawImage now throws when the source image does not overlap, with a useful error message.
Also improved the error messages for IterRows (and added validation to the other IterRows method)
* DrawImage overlap test changed to support RELEASE
The tests on the CI server are run in RELEASE which wrap the expected exception with an ImageProcessingException.
* Adress feedback for DrawImage exception
DrawImage throws an ImageProcessor exception which makes it easier to catch.
And reverted IterRows to use Guard helpers