尝试用噪声、噪声和图像创建噪声图像

Question

我试图在python中创建一些perlin噪声图像，并遇到了一些问题。当我运行我的小脚本时，我得到了一个例外。显然，我并没有掌握图像模块的使用情况，因为我所尝试的每一件事都会导致出现带有“缓冲区不够大”的ValueError异常。

到目前为止，我得到的是：

import numpy
from noise import pnoise2, snoise2
import Image


octaves = 1
freq = 16.0 * octaves
y_max = 5
x_max = 5
imarray = [[0 for x in range(y_max)] for x in range(x_max)]
totalcount = 0

for y in range(y_max):
    for x in range(x_max):
        val = "%s\n" % int(snoise2(x / freq, y / freq, octaves) * 127.0 + 128.0)
        imarray[y][x] = val
        totalcount += 1

arr = numpy.asarray(imarray).astype('uint8')

im = Image.fromarray(arr, 'RGBA')
im.save('./blah.png')

我得到的例外是：

Connected to pydev debugger (build 143.1184)
Traceback (most recent call last):
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydevd.py", line 2407, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydevd.py", line 1798, in run
    launch(file, globals, locals)  # execute the script
  File "/Users/u4234/source/systools/load/noise_test.py", line 26, in <module>
    im = Image.fromarray(arr, 'RGBA')
  File "/Users/u4234/Library/Python/2.7/lib/python/site-packages/PIL-1.1.7-py2.7-macosx-10.10-x86_64.egg/Image.py", line 1902, in fromarray
    return frombuffer(mode, size, obj, "raw", rawmode, 0, 1)
  File "/Users/u4234/Library/Python/2.7/lib/python/site-packages/PIL-1.1.7-py2.7-macosx-10.10-x86_64.egg/Image.py", line 1853, in frombuffer
    core.map_buffer(data, size, decoder_name, None, 0, args)
ValueError: buffer is not large enough

Process finished with exit code 1

Answer 1

问题是，您要求PIL创建一个新的'RGBA'映像，它需要4个通道，但是您只传递一个二维数组，例如一个通道。

如下所示，考虑到这些数组：

arr1 = numpy.zeros((5, 5), dtype=numpy.uint8)  # A single 5x5 channel
arr2 = numpy.zeros((5, 5, 3), dtype=numpy.uint8)  # 3 5x5 channels

创建一个灰度'L'图像：

im = Image.fromarray(arr1, 'L')  # OK
im = Image.fromarray(arr2, 'L')  # ValueError: Too many dimensions.

创建没有alpha通道'RGB'的彩色图像

im = Image.fromarray(arr1, 'RGB')  # ValueError: not enough image data
im = Image.fromarray(arr2, 'RGB')  # OK

注意RGB模式的使用，因为您可能并不关心alpha通道，否则只需向numpy.zeros构造函数添加其他维度。

你可以重写你的代码

arr = numpy.zeros((5, 5, 1), dtype=numpy.uint8)

y_max, x_max, channels = arr.shape

for y in range(y_max):
    for x in range(x_max):
        val = int(snoise2(x / freq, y / freq, octaves) * 127.0 + 128.0)
        arr[y,x,0] = val

im = Image.fromarray(arr, 'L')
im.save('./blah.png')

生成灰度图像。