class ImageSizeValidator(object):
    def __init__(self, min_width=None, min_height=None, max_width=None, max_height=None, min_ratio=None, max_ratio=None):
        self.min_width = min_width
        self.min_height = min_height
        self.max_width = max_width
        self.max_height = max_height
        self.min_ratio = min_ratio
        self.max_ratio = max_ratio

    def __call__(self, value):
        w, h = Image.open(value).size
        ratio = float(w)/float(h)
        errors = []
        error_message_size = "%s is {size} pixel {type}. It's supposed to be {comparison} than {limit}px." % value.name
        error_message_ratio = "%s's width/height ratio is {ratio}. It's supposed to be {comparison} than {limit}" % value.name
        if self.min_width and w < self.min_width:
            errors.append(error_message_size.format(
                size=w, type="wide", comparison="greater", limit=self.min_width)
            )
        if self.min_height and h < self.min_height:
            errors.append(error_message_size.format(
                size=h, type="high", comparison="greater", limit=self.min_height)
            )
        if self.max_width and w > self.max_width:
            errors.append(error_message_size.format(
                size=w, type="wide", comparison="less", limit=self.max_width)
            )
        if self.max_height and h > self.max_height:
            errors.append(error_message_size.format(
                size=h, type="high", comparison="less", limit=self.max_height)
            )
        if self.min_ratio and ratio < self.min_ratio:
            errors.append(error_message_ratio.format(
                ratio=ratio, comparison="greater", limit=self.min_ratio)
            )
        if self.max_ratio and ratio > self.max_ratio:
            errors.append(error_message_ratio.format(
                ratio=ratio, comparison="less", limit=self.max_ratio)
            )
        if errors:
            raise ValidationError(errors)