All the stuff for getting ready to push

assignment0/CHANGELOG

-1/14/19 Create project, implement pseudocode
-1/15/19 Fix bugs with data types and overflows
+1/14:	Create project, implement pseudocode
+1/15:	Fix bugs with data types and overflows
+	Add rounding to make output match example images
+1/23:	Add README, CHANGELOG, Makefile

assignment0/README

+This program applies a sobel filter on PGM images. The program accepts one command line argument, the name of the input file, and writes the output to sobel.pgm.

assignment0/README.txt

-Something or other about how to run the program

assignment0/feddersen_jacob.assignment-0/CHANGELOG

+1/14:	Create project, implement pseudocode
+1/15:	Fix bugs with data types and overflows
+	Add rounding to make output match example images
+1/23:	Add README, CHANGELOG, Makefile

assignment0/feddersen_jacob.assignment-0/Makefile

+sobel: sobel.c
+	gcc -o sobel sobel.c -lm
+
+clean:
+	rm -f sobel sobel.pgm

assignment0/feddersen_jacob.assignment-0/README

+This program applies a sobel filter on PGM images. The program accepts one command line argument, the name of the input file, and writes the output to sobel.pgm.

assignment0/feddersen_jacob.assignment-0/sobel.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <math.h>
+
+/* Do not modify write_pgm() or read_pgm() */
+int write_pgm(char *file, void *image, uint32_t x, uint32_t y)
+{
+  FILE *o;
+
+  if (!(o = fopen(file, "w"))) {
+    perror(file);
+
+    return -1;
+  }
+
+  fprintf(o, "P5\n%u %u\n255\n", x, y);
+
+  /* Assume input data is correctly formatted. *
+   * There's no way to handle it, otherwise.   */
+
+  if (fwrite(image, 1, x * y, o) != (x * y)) {
+    perror("fwrite");
+    fclose(o);
+
+    return -1;
+  }
+
+  fclose(o);
+
+  return 0;
+}
+
+/* A better implementation of this function would read the image dimensions *
+ * from the input and allocate the storage, setting x and y so that the     *
+ * user can determine the size of the file at runtime.  In order to         *
+ * minimize complication, I've written this version to require the user to  *
+ * know the size of the image in advance.                                   */
+int read_pgm(char *file, void *image, uint32_t x, uint32_t y)
+{
+  FILE *f;
+  char s[80];
+  unsigned i, j;
+
+  if (!(f = fopen(file, "r"))) {
+    perror(file);
+
+    return -1;
+  }
+
+  if (!fgets(s, 80, f) || strncmp(s, "P5", 2)) {
+    fprintf(stderr, "Expected P6\n");
+
+    return -1;
+  }
+
+  /* Eat comments */
+  do {
+    fgets(s, 80, f);
+  } while (s[0] == '#');
+
+  if (sscanf(s, "%u %u", &i, &j) != 2 || i != x || j != y) {
+    fprintf(stderr, "Expected x and y dimensions %u %u\n", x, y);
+    fclose(f);
+
+    return -1;
+  }
+
+  /* Eat comments */
+  do {
+    fgets(s, 80, f);
+  } while (s[0] == '#');
+
+  if (strncmp(s, "255", 3)) {
+    fprintf(stderr, "Expected 255\n");
+    fclose(f);
+
+    return -1;
+  }
+
+  if (fread(image, 1, x * y, f) != x * y) {
+    perror("fread");
+    fclose(f);
+
+    return -1;
+  }
+
+  fclose(f);
+
+  return 0;
+}
+
+int main(int argc, char *argv[])
+{
+  if (argc != 2) {
+    fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
+
+    return -1;
+  }
+  
+  uint8_t image[1024][1024];
+  uint8_t out[1024][1024];
+  
+  /* This assumes that the file is a pgm image of size 1024 by 1024 */
+  read_pgm(argv[1], image, 1024, 1024);
+  
+  int8_t Ox[3][3] = {
+    { -1, 0, 1 },
+    { -2, 0, 2 },
+    { -1, 0, 1 }
+  };
+  
+  int8_t Oy[3][3] = {
+    { -1, -2, -1 },
+    { 0, 0, 0 },
+    { 1, 2, 1 }
+  };
+  
+  int r, c, j, i;
+  for (r = 0; r < 1024; r++) {
+    for (c = 0; c < 1024; c++) {
+      
+      /* Handle the cases where the kernel only partially covers the matrix */
+      if (r == 0 || r == 1023 || c == 0 || c == 1023) {
+        out[r][c] = 0;
+        continue;
+      }
+      
+      int x_accumulator = 0;
+      int y_accumulator = 0;
+      
+      for (j = 0; j < 3; j++) {
+        for (i = 0; i < 3; i++) {
+          int img_value = image[r + (j - 1)][c + (i - 1)];
+          x_accumulator = x_accumulator + Ox[j][i] * img_value;
+          y_accumulator = y_accumulator + Oy[j][i] * img_value;
+        }
+      }
+      
+      int result = round(sqrt((x_accumulator * x_accumulator) + (y_accumulator * y_accumulator)));
+      if (result > 255) result = 255;
+      out[r][c] = result;
+    }
+  }
+    
+  /* After processing the image and storing your output in "out", write *
+   * to sobel.pgm.                                                      */
+  write_pgm("sobel.pgm", out, 1024, 1024);
+  
+  return 0;
+}