5 - outofmemory in arrays silently ignored
6 - blending doesn't use premultiplied colors (not porter-duff model)
7 - gradient color ramp is not interpolated in linear space
8 - linear and non-linear image formats behave both linearly
9 - radial gradient circle has got a fixed step instead of
10 proportional to its radius
12 -------------------------
13 Incomplete functionality:
14 -------------------------
17 - proper porter-duff blending
21 - VG_DRAW_IMAGE_STENCIL
22 - _PRE and BW_1 image formats
24 - EGL (image drawing targets)
25 - boundbox / point-on-path / tangent-on-path queries
26 - RENDERING_QUALITY_FASTER == RENDERING_QUALITY_BETTER
28 ---------------------------
29 Possible portability issues
30 ---------------------------
32 - GL_UNSIGNED_INT_8_8_8_8 and other for images
33 - GL_MIRRORED_REPEAT for gradients
34 - GL_CLAMP_TO_EDGE for gradients and pattern paints
35 - GL_CLAMP_TO_BORDER for pattern paints
36 - multitexturing for VG_DRAW_IMAGE_MULTIPLY, VG_DRAW_IMAGE_STENCIL
42 - gradient shaders? antialiasing shader?