1 files changed, 117 insertions, 0 deletions
diff --git a/editor/specialty/ppmspread.c b/editor/specialty/ppmspread.c
new file mode 100644
index 00000000..6753f4fe
--- /dev/null
+++ b/editor/specialty/ppmspread.c
@@ -0,0 +1,117 @@
+/*********************************************************************/
+/* ppmspread -  randomly displace a PPM's pixels by a certain amount */
+/* Frank Neumann, October 1993                                       */
+/* V1.1 16.11.1993                                                   */
+/*                                                                   */
+/* version history:                                                  */
+/* V1.0 12.10.1993    first version                                  */
+/* V1.1 16.11.1993    Rewritten to be NetPBM.programming conforming  */
+/*********************************************************************/
+
+#include <string.h>
+
+#include "ppm.h"
+
+
+
+int
+main(int    argc,
+     char * argv[]) {
+
+    FILE * ifP;
+    int argn, rows, cols;
+    unsigned int row;
+    pixel ** destarray, ** srcarray;
+    pixel * pP;
+    pixel * pP2;
+    pixval maxval;
+    pixval r1, g1, b1;
+    int amount;
+    const char * const usage = "amount [ppmfile]\n        amount: # of pixels to displace a pixel by at most\n";
+
+    /* parse in 'default' parameters */
+    ppm_init(&argc, argv);
+
+    argn = 1;
+
+    /* parse in amount & seed */
+    if (argn == argc)
+        pm_usage(usage);
+    if (sscanf(argv[argn], "%d", &amount) != 1)
+        pm_usage(usage);
+    if (amount < 0)
+        pm_error("amount should be a positive number");
+    ++argn;
+
+    /* parse in filename (if present, stdin otherwise) */
+    if (argn != argc)
+    {
+        ifP = pm_openr(argv[argn]);
+        ++argn;
+    }
+    else
+        ifP = stdin;
+
+    if (argn != argc)
+        pm_usage(usage);
+
+    srcarray = ppm_readppm(ifP, &cols, &rows, &maxval);
+
+    destarray = ppm_allocarray(cols, rows);
+
+    /* clear out the buffer */
+    for (row = 0; row < rows; ++row)
+        memset(destarray[row], 0, cols * sizeof(pixel));
+
+    srand(pm_randseed());
+
+    /* start displacing pixels */
+    for (row = 0; row < rows; ++row) {
+        unsigned int col;
+        pP = &srcarray[row][0];
+
+        for (col = 0; col < cols; ++col) {
+            int const xdis = (rand() % (amount+1)) - ((amount+1) / 2);
+            int const ydis = (rand() % (amount+1)) - ((amount+1) / 2);
+
+            int const xnew = col + xdis;
+            int const ynew = row + ydis;
+
+            /* only set the displaced pixel if it's within the bounds
+               of the image
+            */
+            if (xnew >= 0 && xnew < cols && ynew >= 0 && ynew < rows) {
+                /* displacing a pixel is accomplished by swapping it
+                   with another pixel in its vicinity - so, first
+                   store other pixel's RGB
+                */
+                pP2 = &srcarray[ynew][xnew];
+                r1 = PPM_GETR(*pP2);
+                g1 = PPM_GETG(*pP2);
+                b1 = PPM_GETB(*pP2);
+                /* set second pixel to new value */
+                pP2 = &destarray[ynew][xnew];
+                PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
+                
+                /* now, set first pixel to (old) value of second */
+                pP2 = &destarray[row][col];
+                PPM_ASSIGN(*pP2, r1, g1, b1);
+            } else {
+                /* displaced pixel is out of bounds; leave the old
+                   pixel there
+                */
+                pP2 = &destarray[row][col];
+                PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
+            }
+            ++pP;
+        }
+    }
+
+    ppm_writeppm(stdout, destarray, cols, rows, maxval, 0);
+
+    pm_close(ifP);
+    ppm_freearray(srcarray, rows);
+    ppm_freearray(destarray, rows);
+
+    return 0;
+}