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    <p>I assume you are getting an error like.. <code>TypeError: 'PixelAccess' object is not iterable</code>...?</p> <p>See the <a href="http://effbot.org/imagingbook/image.htm#tag-Image.Image.load" rel="noreferrer">Image.load</a> documentation for how to access pixels..</p> <p>Basically, to get the list of pixels in an image, using <code>PIL</code>:</p> <pre><code>from PIL import Image i = Image.open("myfile.png") pixels = i.load() # this is not a list, nor is it list()'able width, height = i.size all_pixels = [] for x in range(width): for y in range(height): cpixel = pixels[x, y] all_pixels.append(cpixel) </code></pre> <p>That appends every pixel to the <code>all_pixels</code> - if the file is an RGB image (even if it only contains a black-and-white image) these will be a tuple, for example:</p> <pre><code>(255, 255, 255) </code></pre> <p>To convert the image to monochrome, you just average the three values - so, the last three lines of code would become..</p> <pre><code>cpixel = pixels[x, y] bw_value = int(round(sum(cpixel) / float(len(cpixel)))) # the above could probably be bw_value = sum(cpixel)/len(cpixel) all_pixels.append(bw_value) </code></pre> <p>Or to get the luminance (weighted average):</p> <pre><code>cpixel = pixels[x, y] luma = (0.3 * cpixel[0]) + (0.59 * cpixel[1]) + (0.11 * cpixel[2]) all_pixels.append(luma) </code></pre> <p>Or pure 1-bit looking black and white:</p> <pre><code>cpixel = pixels[x, y] if round(sum(cpixel)) / float(len(cpixel)) &gt; 127: all_pixels.append(255) else: all_pixels.append(0) </code></pre> <p>There is probably methods within PIL to do such <code>RGB -&gt; BW</code> conversions quicker, but this works, and isn't particularly slow.</p> <p>If you only want to perform calculations on each row, you could skip adding all the pixels to an intermediate list.. For example, to calculate the average value of each row:</p> <pre><code>from PIL import Image i = Image.open("myfile.png") pixels = i.load() # this is not a list width, height = i.size row_averages = [] for y in range(height): cur_row_ttl = 0 for x in range(width): cur_pixel = pixels[x, y] cur_pixel_mono = sum(cur_pixel) / len(cur_pixel) cur_row_ttl += cur_pixel_mono cur_row_avg = cur_row_ttl / width row_averages.append(cur_row_avg) print "Brighest row:", print max(row_averages) </code></pre>
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    1. POGetting list of pixel values from PIL
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