histogram.py

# http://tophattaylor.blogspot.com/2009/05/python-rgb-histogram.html

# RGB Hitogram
# This script will create a histogram image based on the RGB content of
# an image. It uses PIL to do most of the donkey work but then we just
# draw a pretty graph out of it.
#
# May 2009,  Scott McDonough, www.scottmcdonough.co.uk
#

import Image, ImageDraw

imagepath = "mZXN_1979"  # The image to build the histogram of


histHeight = 120            # Height of the histogram
histWidth = 256             # Width of the histogram
multiplerValue = 1.5        # The multiplier value basically increases
                            # the histogram height so that love values
                            # are easier to see, this in effect chops off
                            # the top of the histogram.
showFstopLines = True       # True/False to hide outline
fStopLines = 5


# Colours to be used
backgroundColor = (51,51,51)    # Background color
lineColor = (102,102,102)       # Line color of fStop Markers
red = (255,60,60)               # Color for the red lines
green = (51,204,51)             # Color for the green lines
blue = (0,102,255)              # Color for the blue lines

##################################################################################


img = Image.open(imagepath)
hist = img.histogram()
histMax = max(hist)                                     comon color
xScale = float(histWidth)/len(hist)                     # xScaling
yScale = float((histHeight)*multiplerValue)/histMax     # yScaling


im = Image.new("RGBA", (histWidth, histHeight), backgroundColor)
draw = ImageDraw.Draw(im)


# Draw Outline is required
if showFstopLines:
    xmarker = histWidth/fStopLines
    x =0
    for i in range(1,fStopLines+1):
        draw.line((x, 0, x, histHeight), fill=lineColor)
        x+=xmarker
    draw.line((histWidth-1, 0, histWidth-1, 200), fill=lineColor)
    draw.line((0, 0, 0, histHeight), fill=lineColor)


# Draw the RGB histogram lines
x=0; c=0;
for i in hist:
    if int(i)==0: pass
    else:
        color = red
        if c>255: color = green
        if c>511: color = blue
        draw.line((x, histHeight, x, histHeight-(i*yScale)), fill=color)
    if x>255: x=0
    else: x+=1
    c+=1

# Now save and show the histogram
im.save('histogram.png', 'PNG')
im.show()