Also make the image not a solid color.

Bug: b/179897703
Change-Id: Ibe2084c4e9f0d9023269218df1ad467bb24a1ae3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52750
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>