how to extract Encoded PNG for each label for building TF Record

[seahawks8]

I have trained several datasets, but am new to using mask
RCNN. I have already built a script to do the following with the output JSON file from labelme

• read image, get height width
• get normalized box coordinates (calculated by reading the points and getting min, max for X and Y)

my question, is how do I get a serialized PNG image for each label?
example
image/object/mask = ["\x89PNG\r\n\x1A\n\x00\x00\x00\rIHDR\...", ...]

[wkentaro]

I think you can use lableme.utils.polygon_to_mask function:

labelme/labelme/utils.py

Lines 69 to 75 in 58693e6

	def polygons_to_mask(img_shape, polygons):
	mask = np.zeros(img_shape[:2], dtype=np.uint8)
	mask = PIL.Image.fromarray(mask)
	xy = list(map(tuple, polygons))
	PIL.ImageDraw.Draw(mask).polygon(xy=xy, outline=1, fill=1)
	mask = np.array(mask, dtype=bool)
	return mask

Then convert the numpy array to a serialized PNG image.

[seahawks8]

Thanks. I tried running that and I just end up with a blank png. A function that exports or shows how to get individual png files for each mask would be ideal. I will keep working on this.

[seahawks8]

Hey so I ended up being able to plot and see the Mask by modifying the function a little bit.
this will draw the PNG just black (background) and the mask will be white.
I wonder if I can just save that polygon png as-is and do the training with that

mask = PIL.Image.fromarray(mask)
xy = list(map(tuple, polygons))
draw = ImageDraw.Draw(mask)
draw.polygon(xy=xy, outline=3, fill=1)
mask.show()

[seahawks8]

Ok i ended up with this to get the serialized PNG

    mask = PIL.Image.fromarray(mask)
    xy = list(map(tuple, polygons))
    draw = ImageDraw.Draw(mask)
    draw.polygon(xy=xy, outline=1, fill=1)
    imgByteArr = io.BytesIO()
    mask.save(imgByteArr, format='PNG')
    imgByteArr = imgByteArr.getvalue()

output will be something along the lines of
b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x07\x80\x00\x00\x048\x08\x00 .....