Bitonal reduction reduces an image to black and white by comparing each pixel to a threshold value. Several modes, defined in ImGearBitonalReductionModes, are available for determining how the red, green, and blue color components of a pixel contribute to its brightness when compared to the threshold value.

If you set Mode to ImGearBitonalReductionModes.WEIGHTED, you may also set the values of Weight1, Weight2, and Weight3. These "weights" are used to determine how much influence the values of the red, green, or blue pixels will have on the reduction. For example, if Weight1 (red) = 255, Weight2 (green) = 0, Weight3 (blue) = 0, the whole reduction will depend on the value of the red pixels. The green and blue pixel values will have "no weight."

Setting Mode to ImGearBitonalReductionModes.GRAYSCALE gives the most weight to the value of green. This optimizes for the perception of the human eye, in which blue is the hardest color to see, and therefore requires the least weight.

A Mode of ImGearBitonalReductionModes.AVERAGE gives equal weight to all three pixel values.

Here are the formulas used by the three different reduction methods:

• GRAYSCALE: value = (red*77 + green*151 + blue*28)/256;
• AVERAGE: value = (red + green + blue)/3;
• WEIGHTED: value = (red*w1 + green*w2 + blue*w3)/(w1 + w2 + w3);

Use the Threshold option to set the threshold value for converting pixels to black or white. If the value, as calculated by one of the above reduction methods, is less than Threshold, the pixels will be set to black; if it is greater than or equal to Threshold, the pixels will be set to white.