I was having issues with the reference image. I’ve got three layers:
- The wing
- The reference image
- The background
The wing and the reference image both have transparency. The wing uses per-pixel alpha so I can have the lines of the veins drawn over the reference image below.
The reference image uses global alpha so I can adjust its brightness.
The background is just black.
(Image from https://blog.furas.pl/pygame-transparent-surface-gb.html)
Just to document what worked in the end:
wing_surf = pygame.Surface(screen.get_size())
wing_surf = wing_surf.convert_alpha(screen)
...
wing_surf.fill((0, 0, 0, 0))
vein_renderer.render_to(wing_surf)
screen.blit(wing_surf)
I’m surprised that first line declaring the wing surface doesn’t need to be:
wing_surf = pygame.Surface(screen.get_size(), masks=pygame.SRCALPHA)
But when I remove the masks parameter it works fine. Removing the call to convert_alpha(), however, breaks the transparency completely.
For the reference image:
reference_surf = pygame.Surface(screen.get_size())
reference_surf.blit(reference_image, REFERENCE_IMAGE_OFFSET)
reference_surf.set_alpha(parameters["reference_alpha"])
...
screen.blit(reference_surf)
I’m using the full screen for the reference image because the original image is huuuge so this is actually faster.
Note that in the actual code the order is:
- Fill the black background
- Blit the reference image
- Blit the wing surface
Generating Both Left and Right Wings #
How about two view modes: the current one which renders one wing and the slider panel and another which renders two wings and no panel?