i&m: add rotation algorithm

2 files changed, 75 insertions, 0 deletions

diff --git a/Year_2/IandM/rotation/data/lena.png b/Year_2/IandM/rotation/data/lena.png
new file mode 100644
index 0000000..59ef68a
--- /dev/null
+++ b/Year_2/IandM/rotation/data/lena.png
diff --git a/Year_2/IandM/rotation/rotation.pde b/Year_2/IandM/rotation/rotation.pde
new file mode 100644
index 0000000..33f79ad
--- /dev/null
+++ b/Year_2/IandM/rotation/rotation.pde
@@ -0,0 +1,75 @@
+void setup() {
+  size(768, 256);
+  PImage img = loadImage("lena.png");
+  img.resize(256, 256);
+  img.filter(GRAY);
+
+  image(img, 0, 0);
+  image(rotate_forward(img, radians(45)), 256, 0);
+  
+  image(inverse_rotate(img, radians(45)), 512, 0);
+}
+
+PImage rotate_forward(PImage I, float theta) {
+  PImage out = createImage(I.width, I.height, RGB);
+
+  out.loadPixels();
+
+  for (int i = 0; i < out.pixels.length; ++i) {
+    out.pixels[i] = color(0);
+  }
+
+  float x, y;
+  float u1, v1;
+
+  for (int u = 0; u < I.width; ++u) {
+    for (int v = 0; v < I.height; ++v) {
+      u1 = u-I.width/2;
+      v1 = v-I.height/2;
+
+      x = u1*cos(theta)-v1*sin(theta);
+      y = u1*sin(theta)+v1*cos(theta);
+
+      x+=I.width/2;
+      y+=I.height/2;
+
+      out.set(round(x), round(y), I.get(u, v));
+    }
+  }
+
+  out.updatePixels();
+
+  return out;
+}
+
+PImage inverse_rotate(PImage I, float theta) {
+  PImage out = createImage(I.width, I.height, RGB);
+
+  out.loadPixels();
+
+  for (int i = 0; i < out.pixels.length; ++i) {
+    out.pixels[i] = color(0);
+  }
+
+  float u, v;
+  float x1, y1;
+
+  for (int x = 0; x < I.width; ++x) {
+    for (int y = 0; y < I.height; ++y) {
+      x1 = x-I.width/2;
+      y1 = y-I.height/2;
+
+      u = x1*cos(theta)+y1*sin(theta);
+      v = -x1*sin(theta)+y1*cos(theta);
+
+      u+=I.width/2;
+      v+=I.height/2;
+
+      out.set(x, y, I.get(round(u), round(v)));
+    }
+  }
+
+  out.updatePixels();
+
+  return out;
+}