AVISynth's ImageWriter is giving blank PNG files

Question

Title says it all really.

BlankClip(length=100,width=1920,height=1080,pixel_type="RGB32",fps=60,color=$ff0000)
\ .ImageWriter("frames/%05d.png",type="png")

Expected result: 100 red images
What I got: 100 transparent images

I've tried the internal ebmp format, and that does give red images, but the "real thing" will have a transparent background and this is flattened to black. That aside, the frames are 7MB each which is just silly (real thing has 5-digit numbers of frames).

Any ideas?

Answer 1

Since you select "RGB32" format for BlankClip, you should provide the alpha channel in "color" parameter as well.

Apparently it's in ARGB format, so you should set it to $ffff0000 (first "ff" is for full opaqueness).