Python3和Wand:尝试保存新映像时的ValueError

Question

我有一个由颜色、名称和值组成的文件。

foo,(255, 212, 201),#FFD4C9
bar,(248, 201, 189),#F8C9BD
baz,(167, 145, 138),#A7918A

我想把它变成200‘m×200’m色块(也就是那个颜色的矩形)，名为foo.gif，bar.gif等等。我尝试用Python 3中的Wand来做这件事，但是我没有运气。

SIZE = 200
with open("foo.txt") as f:
    for line in f:
        if line[0] != "#":
            (name, _, hex_color) = tuple(line.strip().split(","))
            hex_color = hex_color.lower()
            print("{}, {}".format(name, hex_color))

            image_name = "{}.gif".format(name)
            with Drawing() as draw:
                # set draw.fill_color here?
                draw.rectangle(left=0, top=0, width=SIZE, height=SIZE)
                with Image() as image:
                    draw(image)
                    image.format = 'gif'
                    image.save(filename=image_name)

给我

Traceback (most recent call last):
  File "color_swatches.py", line 36, in <module>
    image.format = 'PNG'
  File "/usr/local/lib/python3.4/site-packages/wand/image.py", line 2101, in format
    raise ValueError(repr(fmt) + ' is unsupported format')
ValueError: 'gif' is unsupported format

我还尝试将其保存为jpeg、jpg、png和PNG，但都没有效果。也许是我在凌晨4点25分做这件事的原因。

编辑:我能够用下面的bash脚本完成任务，

#!/bin/bash
while IFS=, read name _ hex
do
    convert -size 200x200 xc:white -fill $hex -draw "rectangle 0,0 200,200" \
        swatches/$name.gif
done < $1

但是我仍然很好奇我对Wand做错了什么。基于省略xc:<color>导致bash脚本失败的问题，我认为添加一行

image.background_color = Color("#fff")

在with Image() as image:行可能工作之后，但是唉，我得到了一个新的错误：

Traceback (most recent call last):
  File "color_swatches.py", line 38, in <module>
    image.background_color = Color("#fff")
  File "/usr/local/lib/python3.4/site-packages/wand/image.py", line 419, in wrapped
    result = function(self, *args, **kwargs)
  File "/usr/local/lib/python3.4/site-packages/wand/image.py", line 1021, in background_color
    self.raise_exception()
  File "/usr/local/lib/python3.4/site-packages/wand/resource.py", line 218, in raise_exception
    raise e
wand.exceptions.WandError: b"wand contains no images `MagickWand-2' @ error/magick-image.c/MagickSetImageBackgroundColor/9541"

Answer 1

第一个错误有点误导，但第二个信息是正确的。Image()构造函数分配魔杖对象，但不分配新图像。正如bash脚本调用-size 200x200一样，您需要在Image()中定义width= & height=。

with Drawing() as draw:
  # set draw.fill_color here? YES
  draw.fill_color = Color(hex_color)
  draw.rectangle(left=0, top=0, width=SIZE, height=SIZE)
  with Image(width=SIZE,height=SIZE) as image:
    draw(image)
    image.format = 'gif'
    image.save(filename=image_name)