raster image of filters-displace-01-f

Verify the basic capability to handle the feDisplacementMap filter node. Six images should appear in 2 rows of 3. On the left in each row a test image of a checker board is displayed. In the middle column is the displacement map. In the right-hand column is the result. All displacement maps are generated as png files with gamma 1.0 and must be interpreted linearly for the proper geometric displacement to occur.

The top row tests a displacement map which displaces each pixel by an amount equivalent to a rotation of 20 degrees around the center of the image. A blue reference rectangle is drawn on the result using an svg transform attribute to mimick the same 20 degree rotation. The edges of the blue rectangle should be parallel to the grid lines in the displaced image. Distortion of the grid pattern such that the grid lines are slightly curved is indicative of improper gamma handling in the viewer.

The bottom row tests a displacement map which distorts the image spherically. The rendered image should match the reference image. In particular the center of the distorted image should be on a gridpoint.

In addition to feDisplacementMap, this test uses the 'feImage' and 'rect' elements. Figure labeling uses the text element. The reference blue rectangle uses fill, fill-opacity, and transform.