(Scroll below for screenshots :-) The last ones are have less 'filter-like' look because they were taken after the matrix-method) Why are trees and grass green? This app uses Renderscript to swap colors (RGB) right inside preveiw, maintaing smooth framerates (above 25fps). Result? Observe nature in light-blue,purple, blue, or red! Using a java only solution required getting images from ImageReader, lopping over pixels, doing the yuv to rgb math, swapping colors, and displaying the resulting pixels on a bitmap, which is then passed back to stream. This was reawlly slow (about 2 frames a second!)

RenderScript provides a built in mapping kernel for color multiplications. Using ScriptIntrinsicColorMatrix, we can make a 4x4 matrix and multiply color vectors with it. We can easily swap color vectors and do color correction. For instance, a 4x4 Identity matrix will keep a color vector unchanged. But say the matrix {{0,1,0,0} {1,0,0,0} {0,0,1,0} {0,0,0,1}} will swap R and G values!

1: An input Allocation receives buffers from stream 2: after allocation is populated, the necessary yuv to rgb conversion is done by a ScriptIntrinsicyuvTorgb (ScriptIntrinsics are essentially pre-built mapping kernels) 3: then the custom kernel "convert" is called. This does the chunck of work. It unpacks the rgb colors to float4. After checking for clicks, it swaps the color elements respectively. 4: the kernel also saturates the final pixels by mixing their respective greyscales with their colors. THe amount of mixing is set by the constant "saturationLevel" (greater than 1.0f saturates the final pixels" 5 After this another intrinsic script is called, ScriptIntrinsicConvolve3x3. This sharpes the images by multiplying a 3x3 chuk of pixels with the convolution matrix. 6 Finally, the final receiveing allocation sends it's surface (on which the ixels are 'drawn') back to the preview stream


Red-Green swap could use some better color correction to red. Or I should upgrade my cam :-)

Video: https://www.youtube.com/watch?v=IxSW7LLedQ0
Got the idea of a video late into winter when all the grass and leaves had turned bad