`img` options and transparency tests

[clydebarrow]

`img` options and transparency tests

[nagyrobi]

Some tests:

        - obj:  # background for test transparency
            id: color_matte
            x: 0
            y: 40
            width: 240
            height: 240
            bg_color: 0x00ffff
            bg_opa: cover
            radius: 0
            pad_all: 0
            border_width: 0
            widgets:
              - img:
                  align: center
                  src: esphome_logo_transparent
                  id: img_transp

with:

image:
  - file: https://esphome.io/_static/made-for-esphome-black-on-transparent.png
    id: esphome_logo_transparent
    resize: 220x72
    type: # as below
    use_transparency: # as below

with type: TRANSPARENT_BINARY (transparency enabled by default) results in:

with type: GRAYSCALE results in (same result with dither: FLOYDSTEINBERG):

with: type: GRAYSCALE and use_transparency: true results in (nothing):

with type: RGB565 results in:

with type: RGB565 and use_transparency: true results in:

with: type: RGB24 results in:

with: type: RGB24 and use_transparency: true results in:

with: type: RGBA (transparency enabled by default) results in:

[nagyrobi]

Supported encodings?

[nagyrobi]

Repeated some of the tests with SVG image instead of PNG:

image:
  - file: https://esphome.io/_static/made-for-esphome-black-on-transparent.svg
    id: esphome_logo_transparent
    resize: 220x72
    type: # as below
    use_transparency: # as below

with type: TRANSPARENT_BINARY (transparency enabled by default) results in:

with: type: GRAYSCALE and use_transparency: true results in (nothing):

with type: RGB565 and use_transparency: true results in:

[nagyrobi]

I think situation is similar to the fonts, LVGL seems to use a proprietary format, and they have online and offline converter tools for images to C arrays: https://lvgl.io/tools/imageconverter

It's two approaches here:

• the command line tool can be used before compile, like pillow or cairo are used (add another type: LVGL with sub-options maybe?)
• some other implementation needs to be done at runtime for #14