1. A method, comprising: transforming an input image comprising pixels having three or more different colors into an output image comprising pixels having two colors, the transforming comprising: identifying two or more contiguous chunks of pixels in the input image at least partially in response to determining that a difference in corresponding color values between adjacent pixels in individual ones of the two or more contiguous chunks of pixels is below a threshold pixel difference value; converting the pixels within the individual ones of the two or more contiguous chunks of the pixels of the input image to: a first color at least partially in response to determining that a number of the pixels within individual ones of the two or more contiguous chunks of pixels is less than or equal to a first size threshold or greater than or equal to a second size threshold, or a second color at least partially in response to determining that a number of pixels within the individual ones of two or more contiguous chunks of pixels is between the first and second size thresholds; and determining whether the output image comprises spam.