1) The document proposes a visual cryptography method that encrypts a color image by randomly partitioning each pixel's R, G, and B values into N images, such that each individual image is unrecognizable but the original image is revealed when all N images are combined. 2) An initial experiment partitioning pixels into two images was unable to sufficiently obscure the original (Mr. Trump's image could still be recognized). 3) Issues were that near-black pixels did not change much between images, allowing the silhouette to be seen, and adjacent near-identical color pixels resulted in recognizable "blocks" across the individual images.

1. Visual Cryptography using Pixels Partition
Yi-Hsin Ma 2018/01/09
• Idea: To encrypt a color image by taking a random N-partition of
each pixel, for R,G,B respectively.
• After the partition, there will be N images. My goal is to make
each picture unrecognized. Only with all picture and combine
them together can we recognize it.
MR_Trump.jpg
First Try
• n is the scale of a pixel, I choose two numbers a & b between 0 to
n using uniform distribution. Then we can split the whole picture
into three parts.
• The result is not good enough. (Mr. Trump can be recognized still.)

2. Problem
• Why can we still recognize Mr. Trump? Below are some problems I
had faced and waiting to be solved.
• The pixel which is nearly black not changing so much. Hence the
silhouette can still be seen.
• Pixels which are adjacent and nearly have the same color would
have same color after the partition , which make people easily to
recognize a “block”.
An Alternative Method
• Multiply each pixel with 19 which is coprime with 255, then mod
255.
• Take that number with partition.

3. After sum up all pictures, I transfer is by multiply 94 ( which is 19^-1 in
Z255 ) mod 255
If losing some pictures and transform back …