read images in python

Replies to This Discussion

Permalink Reply by David Rutten on August 25, 2014 at 4:03am

Can't you use the System.Drawing.Image class? It has width and Height properties and a GetPixel(x,y) method.

Permalink Reply by Vincenzo Reale on August 25, 2014 at 7:14am

Thanks David,

this is a good suggestion, still I am not managing to make it work:

import System

path = "C:\temp\image.jpg"

image = System.Drawing.Image.FromFile(path)

height = System.Drawing.Image.Height(image)
width = System.Drawing.Image.Width(image)

color = System.Drawing.Image.GetPixelFormatSize(height/2,width/2)

a) the path doesn't work, I get an error when I am using "from file" (wrong characters in path)

b) couldn't find getpixel but only getpixelformatsize which looks the wrong command

how should I fix it?

Thanks again

V.

Permalink Reply by djordje on August 25, 2014 at 7:50am

Hi Vincenzo

When using paths in python, use the double backslash characters to separate folders,files. This is because a single backslash is an escape character in python.
Other than that, use the equal character to set or get the property of an object (Width and Height in this case):

import System

path = "D:\\temp\\image.jpg"

bitmap = System.Drawing.Bitmap.FromFile(path)
width = bitmap.Width
height = bitmap.Height
color = System.Drawing.Bitmap.GetPixel(bitmap, width/2, height/2)

Permalink Reply by Vincenzo Reale on August 25, 2014 at 8:01am

Thanks djordje, my mistake, I think you can also use simple "/" and it would work

import System
import rhinoscriptsyntax as rs

path = "C:/temp/image.bmp"

bitmap = System.Drawing.Bitmap.FromFile(path)
width = bitmap.Width
height = bitmap.Height
color = System.Drawing.Bitmap.GetPixel(bitmap, width/2, height/2)

print color

rvalue = color[1]

but when in this case I get the color value which kind of variable is that? I

t is not considered a list in fact the last line is not working, how can I get the values as single numbers from that?

Permalink Reply by djordje on August 25, 2014 at 8:10am

Yes, looks like it supports single forward slashes too. But in the upper example you used a single backslash, and python does not support that. Only double backslashes (that was the point of "wrong characters in path" error message).

As for the last issue: what you got is a Color object. Check for its properties:

avalue = color.A
rvalue = color.R
gvalue = color.G
bvalue = color.B

Permalink Reply by Vincenzo Reale on August 25, 2014 at 8:58am

Thanks a lot again for the support, it definitely works!

Here a piece of code with it implemented and test image:

import System
import rhinoscriptsyntax as rs

def remap(uval,u,h):

start = u[0]
end = u[1]

startt= 0
endt= h

hval = (uval-start)/(end-start) *(endt)

return hval

path = "C:/temp/image2.bmp"
srf = "3e8b01e5-8da8-451e-a86f-060df82a94c9"

bitmap = System.Drawing.Bitmap.FromFile(path)
width = bitmap.Width
height = bitmap.Height

rs.EnableRedraw(False)

listUdomain = rs.SurfaceDomain(srf,0)
listVdomain = rs.SurfaceDomain(srf,1)

floatUstep = (listUdomain[1]-listUdomain[0])/40
floatVstep = (listVdomain[1]-listVdomain[0])/40

for i in rs.frange(listUdomain[0],listUdomain[1],floatUstep):
for j in rs.frange(listVdomain[0],listVdomain[1],floatVstep):

temppt = rs.EvaluateSurface(srf,i,j)

targetwidth = remap(i,listUdomain,width)
targetheight = remap(j,listVdomain,height)


col = System.Drawing.Bitmap.GetPixel(bitmap, abs(targetwidth-1), abs(targetheight-1))


pt = rs.AddSphere(temppt,.3)
rs.ObjectColor(pt,[col.R,col.B,col.G])

rs.EnableRedraw(True)

Permalink Reply by Joy Leelawat on June 21, 2015 at 3:07pm

Hi Vincenzo,

Look great! 

I would like to do the same as you did. Could you explain me a bit about these following lines? 

def remap(uval,u,h):

start = u[0]
end = u[1]

startt= 0
endt= h

hval = (uval-start)/(end-start) *(endt)

return hval