Python/Pillow:如何缩放图像

Question

假设我的图像是2322像素x 4128像素.如何缩放它以使宽度和高度都小于1028px？

我将无法使用Image.resize(https://pillow.readthedocs.io/en/latest/reference/Image.html#PIL.Image.Image.resize)因为这需要我给出新的宽度和高度.我打算做的是(下面的伪代码):

if (image.width or image.height) > 1028:
    if image.width > image.height:
        tn_image = image.scale(make width of image 1028)
        # since the height is less than the width and I am scaling the image
        # and making the width less than 1028px, the height will surely be
        # less than 1028px
    else: #image's height is greater than it's width
        tn_image = image.scale(make height of image 1028)

我猜我需要使用Image.thumbnail,但根据这个例子(http://pillow.readthedocs.org/en/latest/reference/Image.html#create-thumbnails)和这个答案(如何使用PIL调整图像大小并保持其宽高比？),提供宽度和高度以创建缩略图.是否有任何功能可以采用新的宽度或新的高度(不是两者)并缩放整个图像？

Answer 1

Noo需要重新发明轮子,有Image.thumbnail可用的方法:

maxsize = (1028, 1028)
image.thumbnail(maxsize, PIL.Image.ANTIALIAS)

确保最终尺寸不大于给定边界,同时保持纵横比.

指定PIL.Image.ANTIALIAS应用高质量的下采样滤波器以获得更好的调整大小结果,您可能也需要它.

Answer 2

使用Image.resize,但同时计算宽度和高度.

if image.width > 1028 or image.height > 1028:
    if image.height > image.width:
        factor = 1028 / image.height
    else:
        factor = 1028 / image.width
    tn_image = image.resize((int(image.width * factor), int(image.height * factor)))