I need a simple graphics library that supports the following functionality:

Ability to draw polygons (not just rectangles!) with RGBA colors (i.e., partially transparent),
Ability to load bitmap images,
Ability to read current color of pixel in a given coordinate.

Ideally using JavaScript or Python.
Seems like HTML 5 Canvas can handle #2 and #3 but not #1, whereas SVG can handle #1 and #2 but not #3. Am I missing something (about either of these two)? Or are there other alternatives?
PyGame can do all of those things. OTOH, I don't think it embeds into a GUI too well.
Simple graphics API with transparency, polygons, reading image pixels?