Transparent background -t doesn't work

[FilipeMarch]

I was used to do something like:

class Alphabet(Scene):
    def construct(self):
        alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
        for letter in alpha:
            text = TextMobject(letter).set_height(7.5).set_color(BLACK)
            self.add(text)
            self.wait(0.1)
            self.remove(text)

python -m manim script3.py Alphabet -pt

Getting this:

Using the same script and shell command with ManimCE produces this:

[huguesdevimeux]

Thanks for the report.
This is probably due to this line that is not present in manim ce :

https://github.com/3b1b/manim/blob/19e3c97589181ffd43ef14d9169af4e40e054664/manimlib/config.py#L162

This should probably be an easy fix, realted to config. Cc @leotrs

[kolibril13]

I just had a look on it.
If I run manim with -t,

class ABC(Scene):
    def construct(self):
        dot = Dot().set_color(GREEN)
        self.add(dot)
        self.wait(1)
        print(*file_writer_config.items() , sep = "\n")

that tells me

('png_mode', 'RGBA')
('movie_file_extension', '.mov')

So in principle, that is what we want to have.
Also, with the -t tag, manim goes to the scene_file_writer.py into the if statement:

        if file_writer_config["movie_file_extension"] == ".mov":
            # This is if the background of the exported
            # video should be transparent.
            command += [
                "-vcodec",
                "qtrle",
            ]

So it even uses the codec for transparency.
As I have some time tomorrow, can you tell me where I have to look and make changes? :)

[leotrs]

I'm not sure where to make the changes, but if you end up working on that please make sure to add a test for this so there are no regressions.

[leotrs]

Note to self: this will be fixed by #620

[leotrs]

@FilipeMarch would you please kindly pull the latest master branch and try again? I believe this should be fixed now :)

[leotrs]

@kolibril13 has confirmed that the -t flag now works.