On images with light backgrounds, show dark play icon

[brettdh]

Motivation

For items whose cover art is light in color, the white play icon doesn't show up very well:

Plan of action

• Either:
  • Figure out how to detect/set that a background is light
  • When the background is light, use a dark-colored play icon
• Or:
  • Find another method for overlaying the play icon that looks good on dark/light backgrounds