Add drawing line or basic shapes method to Image

[hajimehoshi]

For debugging.

Ideally, it would be possible to develop a prototype without preparing images.

[hajimehoshi]

How about writing texts with an arcade font?

[hajimehoshi]

Let's use shaders to draw lines or circles!

[hajimehoshi]

Path methods:

• BeginPath
• ClosePath
• MoveTo
• LineTo
• BezierCurveTo
• QuadraticCurveTo
• Arc
• ArcTo
• Ellipse
• Rect
• Clip?

Image methods:

• FillPath
• StrokePath (gl.LINE_STRIP)

[hajimehoshi]

It sounds nice if these are in exp (experimental) package.

[hajimehoshi]

It seems hard to implement filling in a polygon (especially on WebGL).

• DrawPoints
• DrawLines
• DrawBezierCurves
• DrawQuadraticCurves
• DrawArcs
• DrawPies
• DrawEllipses
• DrawRects
• FillPies
• FillEllipses
• FillRects

How about cardinal spline?

[hajimehoshi]

Actually added:

• DrawLine
• DrawLines
• DrawRect
• DrawRects
• FillRect
• FillRects

I think that's enough so far for v1.2. I'll add other methods if required.

[hajimehoshi]

It seems hard to implement filling in a polygon (especially on WebGL).

NOTE: I found it's possible if I use stencil buffers. In this case, the filling algorithm would be even-odd.