Question

我似乎无法弄清楚如何使用我的灰度功能并改变它以给我假色。我知道我需要将每种颜色（R，G，B）分解为范围，然后根据每种颜色的范围分配颜色。有没有人知道这是如何工作的？

def grayscale(pic):
    (width,height) = pic.size
    for y in range (height):
        for x in range(width):
            pix = cp.getpixel((x,y))
            (r, g, b) = pix
            avg = (r + g + b)//3
            newPix = (avg, avg, avg)
            cp.putpixel((x,y),newPix)
    return cp

Answer 1

由于您从未在评论中回答我的后续问题，因此我做了一些猜测并实施了一些内容，以说明如何仅使用PIL（或pillow来完成）模块。

from PIL import Image
from PIL.ImageColor import getcolor, getrgb
from PIL.ImageOps import grayscale

try:
    xrange
except NameError:  # Python 3.
    xrange = range

def falsecolor(src, colors):
    if Image.isStringType(src):  # File path?
        src = Image.open(src)
    if src.mode not in ['L', 'RGB', 'RGBA']:
        raise TypeError('Unsupported source image mode: {}'.format(src.mode))
    src.load()

    # Create look-up-tables (luts) to map luminosity ranges to components
    # of the colors given in the color palette.
    num_colors = len(colors)
    palette = [colors[int(i/256.*num_colors)] for i in xrange(256)]
    luts = (tuple(c[0] for c in palette) +
            tuple(c[1] for c in palette) +
            tuple(c[2] for c in palette))

    # Create grayscale version of image of necessary.
    l = src if Image.getmodebands(src.mode) == 1 else grayscale(src)

    # Convert grayscale to an equivalent RGB mode image.
    if Image.getmodebands(src.mode) < 4:  # Non-alpha image?
        merge_args = ('RGB', (l, l, l))  # RGB version of grayscale.

    else:  # Include copy of src image's alpha layer.
        a = Image.new('L', src.size)
        a.putdata(src.getdata(3))
        luts += tuple(xrange(256))  # Add a 1:1 mapping for alpha values.
        merge_args = ('RGBA', (l, l, l, a))  # RGBA version of grayscale.

    # Merge all the grayscale bands back together and apply the luts to it.
    return Image.merge(*merge_args).point(luts)

if __name__ == '__main__':
    R, G, B = (255,   0,   0), (  0, 255,   0), (  0,   0, 255)
    C, M, Y = (  0, 255, 255), (255,   0, 255), (255, 255,   0)
    filename = 'test_image.png'

    # Convert image into falsecolor one with 4 colors and display it.
    falsecolor(filename, [B, R, G, Y]).show()

下面是一个复合材料，显示了RGB测试图像，中间内部256级灰度图像，以及将其更改为假色的最终结果，仅由四种颜色组成（每种颜色代表64级强度）：

这是另一个复合材料，只是这次显示将已经灰度的图像转换为4种假色的相同调色板。

这样的事情是你想要做的吗？

Answer 2

看起来你要做的就是确定每个像素的平均亮度，并使每个像素变灰。我会使用原生图像功能，或者如果你想操纵单个像素，至少使用numpy而不是嵌套for循环。例如：

from PIL import Image, ImageDraw
import numpy as np

def makeGrey():
    W = 800
    H = 600
    img = Image.new('RGB', (W, H))
    draw = ImageDraw.Draw(img)

    draw.rectangle((0, H * 0 / 3, W, H * 1 / 3), fill=(174, 28, 40), outline=None)
    draw.rectangle((0, H * 1 / 3, W, H * 2 / 3), fill=(255, 255, 255), outline=None)
    draw.rectangle((0, H * 2 / 3, W, H * 3 / 3), fill=(33, 70, 139), outline=None)

    img.show()

    pixels = np.array(img.getdata())
    avg_pixels = np.sum(pixels, axis=1) / 3
    grey_img = avg_pixels.reshape([H, W])

    img2 = Image.fromarray(grey_img)
    img2.show()

if __name__ == '__main__':
    makeGrey()

如何使用PIL将灰度转换为假色？

2 个答案: