modules/masking.py

from PIL import Image, ImageFilter, ImageOps


def get_crop_region(mask, pad=0):
    """finds a rectangular region that contains all masked ares in an image. Returns (x1, y1, x2, y2) coordinates of the rectangle.
    For example, if a user has painted the top-right part of a 512x512 image", the result may be (256, 0, 512, 256)"""
    
    h, w = mask.shape

    crop_left = 0
    for i in range(w):
        if not (mask[:, i] == 0).all():
            break
        crop_left += 1

    crop_right = 0
    for i in reversed(range(w)):
        if not (mask[:, i] == 0).all():
            break
        crop_right += 1

    crop_top = 0
    for i in range(h):
        if not (mask[i] == 0).all():
            break
        crop_top += 1

    crop_bottom = 0
    for i in reversed(range(h)):
        if not (mask[i] == 0).all():
            break
        crop_bottom += 1

    return (
        int(max(crop_left-pad, 0)),
        int(max(crop_top-pad, 0)),
        int(min(w - crop_right + pad, w)),
        int(min(h - crop_bottom + pad, h))
    )


def expand_crop_region(crop_region, processing_width, processing_height, image_width, image_height):
    """expands crop region get_crop_region() to match the ratio of the image the region will processed in; returns expanded region
    for example, if user drew mask in a 128x32 region, and the dimensions for processing are 512x512, the region will be expanded to 128x128."""

    x1, y1, x2, y2 = crop_region

    ratio_crop_region = (x2 - x1) / (y2 - y1)
    ratio_processing = processing_width / processing_height

    if ratio_crop_region > ratio_processing:
        desired_height = (x2 - x1) / ratio_processing
        desired_height_diff = int(desired_height - (y2-y1))
        y1 -= desired_height_diff//2
        y2 += desired_height_diff - desired_height_diff//2
        if y2 >= image_height:
            diff = y2 - image_height
            y2 -= diff
            y1 -= diff
        if y1 < 0:
            y2 -= y1
            y1 -= y1
        if y2 >= image_height:
            y2 = image_height
    else:
        desired_width = (y2 - y1) * ratio_processing
        desired_width_diff = int(desired_width - (x2-x1))
        x1 -= desired_width_diff//2
        x2 += desired_width_diff - desired_width_diff//2
        if x2 >= image_width:
            diff = x2 - image_width
            x2 -= diff
            x1 -= diff
        if x1 < 0:
            x2 -= x1
            x1 -= x1
        if x2 >= image_width:
            x2 = image_width

    return x1, y1, x2, y2


def fill(image, mask):
    """fills masked regions with colors from image using blur. Not extremely effective."""

    image_mod = Image.new('RGBA', (image.width, image.height))

    image_masked = Image.new('RGBa', (image.width, image.height))
    image_masked.paste(image.convert("RGBA").convert("RGBa"), mask=ImageOps.invert(mask.convert('L')))

    image_masked = image_masked.convert('RGBa')

    for radius, repeats in [(256, 1), (64, 1), (16, 2), (4, 4), (2, 2), (0, 1)]:
        blurred = image_masked.filter(ImageFilter.GaussianBlur(radius)).convert('RGBA')
        for _ in range(repeats):
            image_mod.alpha_composite(blurred)

    return image_mod.convert("RGB")