Region Segmentation error in my sample image

[leonardorame]

Hi!, I'm trying to test the example region_segmentation with the image at the bottom of this post (when loaded in LiveBook I get this info: 1.png, 697x800 8-bit unsigned integer, 3 bands, sRGB).

First I add the "Hola Mundo" text at the top left of the image, to simulate a couple of artifacts:

png = Image.open!("/home/leonardo/LiveBooks/files/1.png")
{:ok, text} = Image.Text.simple_text("Hola mundo",
  height: Image.height(png),
  width: Image.width(png),
  text_fill_color: :white, 
  font_size: 24,
  dpi: 200,
  y: 10,
  x: 10)   
{:ok, img} = Image.compose(png, text) 
{:ok, img} = Image.resize(img, 0.60)   
img |> Image.to_colorspace!(:srgb)

That results in:

Then, using the resulting image I follow the region_segmentation example, but at the end of it I get:
** (ArgumentError) operation build: linear: vector must have 1 or 4 elements

Could you check it with my image?.

[kipcole9]

You'll want to flatten your image (remove the alpha band) before you start processing it. So change:

img |> Image.to_colorspace!(:srgb)

to

img |> Image.to_colorspace!(:srgb) |> Image.flatten()

On my system that produces the expected result. Let me know how it looks on your end?

[kipcole9]

It would certainly be possible to work with an image that has an alpha band but its more complex and for your use case I don't believe it adds any value.

[leonardorame]

Mm, I'm still getting the same error. But don't worry, the relevant part for me is getting the bounding boxes of artifacts, and that works as expected with my image.

[kipcole9]

Thats surprising given I'm using your exact code without error (after using Image.flatten(png). I'm happy to keep digging. Are you able to share your livebook?

[leonardorame]

Maybe you are not using exactly the same image, I attached it here, but I don't know if Github changes the original file.

[kipcole9]

I used your exact image, and got the same error you did. Adding Image.flatten() fixed it because it reduces the image to 3 bands by blending in any alpha band.