how real_label can convert rgb mask image to one-channel id mask?

[LilyDaytoy]

Hi, thanks for this wonderful work!
I would like to ask that, in demo.py,

    def read_label(self, label_name, squeeze_idx=None):
        label_path = os.path.join(self.label_root, self.seq_name, label_name)
        label = Image.open(label_path)
        label = np.array(label, dtype=np.uint8)
        if self.single_obj:
            label = (label > 0).astype(np.uint8)
        elif squeeze_idx is not None:
            squeezed_label = label * 0
            for idx in range(len(squeeze_idx)):
                obj_id = squeeze_idx[idx]
                if obj_id == 0:
                    continue
                mask = label == obj_id
                squeezed_label += (mask * idx).astype(np.uint8)
            label = squeezed_label
        return label

why the rgb mask goes through the codes below

label = Image.open(label_path)
label = np.array(label, dtype=np.uint8)

and can be converted to a one-channel id mask? How should I enocode a mask image so that I could achieve this effect? Thanks!

[z-x-yang]

The mask files are not in rgb but are one-channel images, whose colors are from the attached palette information.

[LilyDaytoy]

Ohh, I see, the mask is 'P' mode pillow image, thanks!