1 files changed, 114 insertions, 0 deletions
diff --git a/src/aliasing/filter.cpp b/src/aliasing/filter.cpp
new file mode 100644
index 0000000..1732dc4
--- /dev/null
+++ b/src/aliasing/filter.cpp
@@ -0,0 +1,114 @@
+#include "raytracer/raytracer.h"
+
+/**
+ * Extra credit.
+ * Code from filter project to offer antialiasing.
+ * FilterBlur at bottom of file used in raytracer.
+ */
+
+enum KERNEL_CHANNEL {
+    RED,
+    GREEN,
+    BLUE,
+    NONE=-1,
+};
+
+struct Kernel1D {
+    std::function<double(double, KERNEL_CHANNEL)> getWeight;
+    double radius;
+};
+
+enum CONVOLVE_DIRECTION {
+    HORIZONTAL,
+    VERTICAL
+};
+
+RGBA getPixelWrapped(std::vector<RGBA> &data, int width, int height, int x, int y) {
+    int newX = (x < 0) ? x + width  : x % width;
+    int newY = (y < 0) ? y + height : y % height;
+    return data[width * newY + newX];
+}
+
+std::uint8_t floatToUint8(float x) {
+    x = std::min(255.f, x);
+    return round(x * 255.f);
+}
+
+std::vector<RGBA> convolve1D(std::vector<RGBA> data, int width, int height, Kernel1D kernel, CONVOLVE_DIRECTION direction) {
+    // need to assign then set, since the direction could be either way
+    std::vector<RGBA> result;
+    result.assign(width*height, RGBA{0, 0, 0, 255});
+
+    // get the order of the for loop, based on the bound
+    int outerBound = direction == CONVOLVE_DIRECTION::HORIZONTAL ? height : width;
+    int innerBound = direction == CONVOLVE_DIRECTION::HORIZONTAL ? width : height;
+
+    for (int i = 0; i < outerBound; i++) {
+        for (int j = 0; j < innerBound; j++) {
+            float redAcc = 0.f, greenAcc = 0.f, blueAcc = 0.f;
+            for (int k = -kernel.radius; k <= kernel.radius; k++) {
+                // get the weight for each channel, at this kernel index
+                double rWeight = kernel.getWeight(k, KERNEL_CHANNEL::RED);
+                double gWeight = kernel.getWeight(k, KERNEL_CHANNEL::GREEN);
+                double bWeight = kernel.getWeight(k, KERNEL_CHANNEL::BLUE);
+
+                // determine the pixel location on the canvas
+                int pixelX = direction == CONVOLVE_DIRECTION::HORIZONTAL ? j + k : i;
+                int pixelY = direction == CONVOLVE_DIRECTION::HORIZONTAL ? i : j + k;
+
+                // get the pixel to compute this inner index of convolution.
+                //  if out of bounds, get the wrapped
+                RGBA pixel;
+                if (pixelX < 0 || pixelX >= width || pixelY < 0 || pixelY >= height)
+                    pixel = getPixelWrapped(data, width, height, pixelX, pixelY);
+                else
+                    pixel = data.at(width * pixelY + pixelX);
+
+                // sum the weights on each channel
+                redAcc += rWeight * pixel.r/255.f;
+                greenAcc += gWeight * pixel.g/255.f;
+                blueAcc += bWeight * pixel.b/255.f;
+            }
+
+            // get location then set the pixel into the result
+            int pixelOnCanvas = direction == CONVOLVE_DIRECTION::HORIZONTAL ? width * i + j : width * j + i;
+            result[pixelOnCanvas] = RGBA{floatToUint8(redAcc), floatToUint8(greenAcc), floatToUint8(blueAcc), 255};
+        }
+    }
+
+    return result;
+}
+
+double triangleFilter(double x, double a) {
+    double radius;
+    if (a < 1) {
+        radius = 1/a;
+    } else {
+        radius = 1;
+    }
+
+    if (x < -radius || x > radius)
+        return 0;
+
+    return (1 - std::fabs(x)/radius) / radius;
+}
+
+void RayTracer::filterBlur(RGBA *imageData, int width, int height, float blurRadius) {
+    // make triangle filter
+    // note: 1/blurRadius for the "radius" of the filter will normalize the area under it to 1
+    Kernel1D triangleKernel;
+    triangleKernel.radius = blurRadius;
+    triangleKernel.getWeight = [blurRadius](double x, int c) { return triangleFilter(x, 1/blurRadius); };
+
+    std::vector<RGBA> data{};
+    for (int i = 0; i < width*height; i++) {
+        data.push_back(imageData[i]);
+    }
+
+    std::vector<RGBA> res = convolve1D(data, width, height, triangleKernel, HORIZONTAL);
+    res = convolve1D(res, width,height, triangleKernel, VERTICAL);
+
+    for (int i = 0; i < res.size(); i++) {
+        imageData[i] = res[i];
+    }
+}