Convert an rgb mask image to coco json polygon format

问题

I annotated images using PixelAnnotationTool provided here: https://github.com/abreheret/PixelAnnotationTool and using the provided dictionary:

{
    "labels": {
        "unlabeled": {
            "categorie": "void",
            "color": [
                0,
                0,
                0
            ],
            "id": 0,
            "id_categorie": 0,
            "name": "unlabeled"
        },
        "bicycle_motorcycle": {
            "categorie": "bicycle_motorcycle",
            "color": [
                119,
                11,
                32
            ],
            "id": 1,
            "id_categorie": 1,
            "name": "bicycle_motorcycle"
        },
        "bus": {
            "categorie": "bus",
            "color": [
                102,
                51,
                0
            ],
            "id": 2,
            "id_categorie": 2,
            "name": "bus"
        },

.... }

I want to convert these RGB masks into json polygon format so that I can use them in Mask R-CNN. How to do this?

回答1:

Here's a python function that will take in a mask Image object and return a dictionary of sub-masks, keyed by RGB color.

from PIL import Image # (pip install Pillow)

def create_sub_masks(mask_image):
    width, height = mask_image.size

    # Initialize a dictionary of sub-masks indexed by RGB colors
    sub_masks = {}
    for x in range(width):
        for y in range(height):
            # Get the RGB values of the pixel
            pixel = mask_image.getpixel((x,y))[:3]

            # If the pixel is not black...
            if pixel != (0, 0, 0):
                # Check to see if we've created a sub-mask...
                pixel_str = str(pixel)
                sub_mask = sub_masks.get(pixel_str)
                if sub_mask is None:
                   # Create a sub-mask (one bit per pixel) and add to the dictionary
                    # Note: we add 1 pixel of padding in each direction
                    # because the contours module doesn't handle cases
                    # where pixels bleed to the edge of the image
                    sub_masks[pixel_str] = Image.new('1', (width+2, height+2))

                # Set the pixel value to 1 (default is 0), accounting for padding
                sub_masks[pixel_str].putpixel((x+1, y+1), 1)

    return sub_masks

Once you have the masks you can use imantics to convert it to COCO

来源：https://stackoverflow.com/questions/54802089/convert-an-rgb-mask-image-to-coco-json-polygon-format