Mandelbrot Fractal image output to ppm file (Python recipe) by FB36

ActiveState Code (http://code.activestate.com/recipes/579006/)

This is how each pixel can be set directly:

# Mandelbrot Fractal image output to ppm file
# FB - 20150117
imgx = 512; imgy = 512
xa = -2.0; xb = 1.0
ya = -1.5; yb = 1.5
maxIt = 256
rgbPixels = [chr(0) + chr(0) + chr(0) for p in range(imgx * imgy)]
for ky in range(imgy):
    for kx in range(imgx):
        c = complex(xa + (xb - xa) * kx / imgx, ya + (yb - ya) * ky / imgy)
        z = complex(0.0, 0.0)
        for i in range(maxIt):
            z = z * z + c
            if abs(z) >= 2.0:
                break
        rgbPixels[kx + ky * imgy] = chr(i % 4 * 64) + chr(i % 8 * 32) + chr(i % 16 * 16)

f = open("ManFr.ppm", "wb")
f.write("P6\n")
f.write("# ManFr.ppm\n") # comment
f.write(str(imgx) + " " + str(imgy) + "\n")
f.write(str(255) + "\n") # max color value
f.write("".join(rgbPixels))
f.close()

PPM image processing example:

# PPM Image Processing Example
# FB - 20150117
def LoadPPM(filename):
    f = open(filename, "rb")
    lines = []
    while True:
        line = f.readline().strip()
        if line == "255": # max color value line
            break
        if not line.startswith("#"): # skip comment line(s)
            lines.append(line)
    rgbPixels = f.read()
    f.close()
    imgximgy = lines[1].split(" ")
    imgx = int(imgximgy[0]); imgy = int(imgximgy[1])
    return (imgx, imgy, rgbPixels)

def SavePPM(imgx, imgy, rgbPixels, filename):
    f = open(filename, "wb")
    f.write("P6\n")
    f.write(str(imgx) + " " + str(imgy) + "\n")
    f.write(str(255) + "\n") # max color value
    f.write(rgbPixels)
    f.close()

def ProcessImage(imgx, imgy, rgbPixels):
    rgbPixelsList = []
    for i in range(len(rgbPixels) / 3):
        rgbPixelsList.append(rgbPixels[i * 3 : i * 3 + 3])
    for ky in range(imgy):
        for kx in range(imgx):
            rgb = rgbPixelsList[kx + ky * imgy]
            r = ord(rgb[0]); g = ord(rgb[1]); b = ord(rgb[2])
            r = 255 - r; g = 255 - g; b = 255 - b # reverse colors
            a = (r + g + b) / 3; r = a; g = a; b = a # convert to grayscale
            rgbPixelsList[kx + ky * imgy] = chr(r) + chr(g) + chr(b)    
    return "".join(rgbPixelsList)

# TEST
(imgx, imgy, rgbPixels) = LoadPPM("ManFr.ppm")
rgbPixels = ProcessImage(imgx, imgy, rgbPixels)
SavePPM(imgx, imgy, rgbPixels, "ManFr2.ppm")