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[英]How to check whether a jpeg image is color or grayscale using only Python PIL? (not using OpenCV)
[英]How to turn grayscale into false color using PIL?
我似乎無法弄清楚如何使用我的灰度函數並將其更改為給我假顏色。 我知道我需要將每種顏色(R、G、B)分成多個范圍,然后根據每種顏色的范圍分配顏色。 有誰知道這是如何工作的?
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
由於您從未在評論中回答我的最后一個后續問題,因此我做了一些猜測並實現了一些東西來說明如何僅使用PIL
(或pillow
)模塊來完成它。
簡而言之,代碼將圖像轉換為灰度,將產生的 0% 到 100% 亮度(強度)像素范圍划分為大小相等的子范圍,然后從調色板中為每個子范圍分配一種顏色。
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()
下面是一張合成圖,顯示了 RGB 測試圖像、中間的內部 256 級灰度圖像,以及將其更改為僅包含四種顏色(每種顏色代表 64 級強度范圍)的假彩色的最終結果:
這是另一個合成圖,只是這次顯示了將已經灰度化的圖像轉換為 4 種假色的相同調色板。
你想做這樣的事情嗎?
看起來您要做的就是確定每個像素的平均亮度,並使每個像素變灰。 我會為此使用本機 Image 功能,或者如果您想操作單個像素,至少使用numpy
而不是嵌套的for
循環。 例子:
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()
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