Can extra functions be exposed

[mrpotes]

It's been a long time since I used C/C++, and I'm pretty new to Python, but I notice that inc/microbit/microbitimage.h has a function declaration, microbit_image_for_char, that sounds like just what I need - could it be exposed as a python function for turning a single character into the LED image string, or maybe a string into an array of LED image strings?

Thanks :)

[ZanderBrown]

is SHOW 'a' not sufficient?

[deshipu]

You can do better:

from microbit import Image

letter_a = Image('A')

[mrpotes]

No, we need to modify the LED arrangement so that it will read correctly in a mirror, but start from a normal letter representation to do so, so it would be great not to have to reproduce something the microbit already knows how to do.

[deshipu]

Why do you need a string for it? Can't you invert the image?

[mrpotes]

@deshipu does Image('A') work? The docs say:

If string is used, it has to consist of digits 0-9 arranged into lines, describing the image

[deshipu]

If there was only some way of checking if it works...

[mrpotes]

@deshipu we want the text to scroll just like it does if you use the scroll function, but mirrored. As I understand it, invert inverts the brightness of the image (0 -> 9, 1 -> 8, etc), it doesn't do flip horizontally (or vertically, for that matter)

[mrpotes]

If there was only some way of checking if it works...

If only the microbits weren't locked away in a cupboard at school, you mean?

[deshipu]

Yes, you will have to write the function that mirrors the image yourself. But it should be easier and faster with an image than with a string.

An efficient way to do it is to only iterate over half of the image, and swap its pixels with the other half. This way you can do it in place, without having to create a new image and allocate memory. Something like:

def mirror(image):
    for y in range(image.height()):
        for x in range(image.width() // 2):
            other_x = image.width() - x -1
            pixel = image.get_pixel(x, y)
            image.set_pixel(x, y, image.get_pixel(other_x, y))
            image.set_pixel(other_x, y, pixel)

[deshipu]

If only the microbits weren't locked away in a cupboard at school, you mean?

I'm sorry, I didn't think.

[mrpotes]

I'm sorry, I didn't think.

No problem :)

So if Image('A') works that's great, then I'm thinking something like (pseudo code as I haven't worked out all of this in python):

def scrollMirrored(str):
  show(
    chars(str)
      .map(c: repr(Image(c)).split(':'))
      .zip()
      .map(str_join)
      .map(s: s.reverse)
      .map(s: chars(str).slidingWindow(5))
      .zip()
      .map(arr: arr.join(':')))