def plain_white(height, width):
    return Image.new("L", (width, height), 255).convert("RGBA")

def gaussian_noise(height, width):
    # 创建一个白色图
    image = np.ones((height, width)) * 255
    # 添加高斯噪声
    cv2.randn(image, 235, 10)
    # 从opencv转PIL.Image ，带有透明度
    return Image.fromarray(image).convert("RGBA")

def quasicrystal(height, width):
    image = Image.new("L", (width, height))
    pixels = image.load()
    frequency = rnd.random() * 30 + 20  # frequency
    phase = rnd.random() * 2 * math.pi  # phase
    rotation_count = rnd.randint(10, 20)  # of rotations
    for kw in range(width):
        y = float(kw) / (width - 1) * 4 * math.pi - 2 * math.pi
        for kh in range(height):
            x = float(kh) / (height - 1) * 4 * math.pi - 2 * math.pi
            z = 0.0
            for i in range(rotation_count):
                r = math.hypot(x, y)
                a = math.atan2(y, x) + i * math.pi * 2.0 / rotation_count
                z += math.cos(r * math.sin(a) * frequency + phase)
            c = int(255 - round(255 * z / rotation_count))
            pixels[kw, kh] = c  # grayscale
    return image.convert("RGBA")

def image(height, width, image_dir):
    images = os.listdir(image_dir)
    if len(images) > 0:
        pic = Image.open(
            os.path.join(image_dir, images[rnd.randint(0, len(images) - 1)])
        )
        # 不失真resize
        if pic.size[0] < width:
            pic = pic.resize(
                [width, int(pic.size[1] * (width / pic.size[0]))], Image.ANTIALIAS
            )
        if pic.size[1] < height:
            pic = pic.resize(
                [int(pic.size[0] * (height / pic.size[1])), height], Image.ANTIALIAS
            )
        if pic.size[0] == width:
            x = 0
        else:
            x = rnd.randint(0, pic.size[0] - width)
        if pic.size[1] == height:
            y = 0
        else:
            y = rnd.randint(0, pic.size[1] - height)
        return pic.crop((x, y, x + width, y + height))
    else:
        raise Exception("No images where found in the images folder!")