从JPEG或png文件获取绘图数据

Question

我正在编写一个从图形(JPEG)中获取绘图数据的程序.垂直轴是对数的.我成功地制作了一个程序,将水平和垂直轴理解为线性(不是对数),请参阅下面的代码:

%matplotlib inline

from PIL import Image
from scipy import *
from pylab import *

im = array(Image.open('fig1.jpg'))

hh = im.shape[0]
ww = im.shape[2]

imshow(im)    
print(im[100,0,:])

Col = array([255,0,0])#?
bnd = 30

yax = linspace(0.5,2e-4,hh)
xax = linspace(1,14,ww)

for i in range(hh):
    for j in range(ww):
        im[i,j,:] = 255*(any(im[i,j,:]>Col+bnd) or any(im[i,j,:]<Col-bnd))

mapim = abs(im[:,:,0]/255-1).astype(bool)

yval = array([average(yax[mapim[:,t]]) for t in range(ww)])

rlt = interp(range(100),xax,yval)

我不知道如何修改它以使其理解对数轴.请帮我.

Answer 1

您只需将 y max 和 min 转换为对数刻度：

ymax_lin = log10(0.5)
ymin_lin = log10(2e-4)

yax = linspace(ymax_lin,ymin_lin,hh)

yval并在最后将值转换回线性：

yval = 10**yval

完整的工作代码在这里：

%matplotlib inline

from PIL import Image
from scipy import *
from pylab import *

im = array(Image.open('fig1.jpg'))

hh = im.shape[0]
ww = im.shape[1]

imshow(im)    
print(im[100,0,:])

Col = array([255,0,0])
bnd = 30


ymax_lin = log10(0.5)
ymin_lin = log10(2e-4)

yax = linspace(ymax_lin,ymin_lin,hh)
xax = linspace(1,14,ww)

for i in range(hh):
    for j in range(ww):
        im[i,j,:] = 255*(any(im[i,j,:]>Col+bnd) or any(im[i,j,:]<Col-bnd))

mapim = abs(im[:,:,0]/255-1).astype(bool)


yval = array([average(yax[mapim[:,t]]) for t in range(ww)])

yval = 10**yval

rlt = interp(range(100),xax,yval)