[hackers] [farbfeld] Optimize ff2ppm(1) || FRIGN

[git]

commit f0a4ce113d0e9dc50110a0ad9e98433d05aa2307
Author:     FRIGN <d...@frign.de>
AuthorDate: Mon Mar 21 22:26:37 2016 +0100
Commit:     FRIGN <d...@frign.de>
CommitDate: Mon Mar 21 22:26:37 2016 +0100

    Optimize ff2ppm(1)
    
    use the proper multiplication factors :)

diff --git a/ff2ppm.c b/ff2ppm.c
index 7f6aa61..09eb346 100644
--- a/ff2ppm.c
+++ b/ff2ppm.c
@@ -23,45 +23,33 @@ int
 main(int argc, char *argv[])
 {
        size_t rowlen;
-       uint32_t hdr[4], width, height, i, j, k;
-       uint16_t *row, mr = 0xffff, mg = 0xffff, mb = 0xffff;
+       uint64_t a;
+       uint32_t hdr[4], width, height, i, j, k, l;
+       uint16_t *row, mask[3] = { 0xffff, 0xffff, 0xffff };
        uint8_t *rowout;
-       char *color;
-       unsigned int r = 0xff, g = 0xff, b = 0xff;
-       float a;
+       char *color, colfmt[] = "%#x%#x%#x";
+       unsigned int collen, col[3], colfac;
 
        argv0 = argv[0];
        ARGBEGIN {
        case 'b':
-               for (color = EARGF(usage()); *color && *color == '#'; color++)
-                       ;
-
-               switch (strlen(color)) {
-               case 3:
-                       if (sscanf(color, "%1x%1x%1x", &r, &g, &b) != 3)
-                               usage();
-                       mr = (r | r << 4) * 257;
-                       mg = (g | g << 4) * 257;
-                       mb = (b | b << 4) * 257;
-                       break;
-               case 6:
-                       if (sscanf(color, "%2x%2x%2x", &r, &g, &b) != 3)
-                               usage();
-                       mr = r * 257;
-                       mg = g * 257;
-                       mb = b * 257;
-                       break;
-               case 12:
-                       if (sscanf(color, "%4x%4x%4x", &r, &g, &b) != 3)
-                               usage();
-                       mr = r;
-                       mg = g;
-                       mb = b;
-                       break;
-               default:
+               color = EARGF(usage());
+               if (color[0] == '#') {
+                       color++;
+               }
+               collen = strlen(color);
+               if (collen != 3 && collen != 6 && collen != 12) {
+                       usage();
+               }
+               colfmt[1] = colfmt[4] = colfmt[7] = ((collen / 3) - '0');
+               if (sscanf(color, colfmt, col, col + 1, col + 2) != 3) {
                        usage();
                }
-               break;
+               /* UINT16_MAX / 255 = 257; UINT16_MAX / 15 = 4369 */
+               colfac = (collen == 3) ? 4369 : (collen == 6) ? 257 : 1;
+               for (i = 0; i < 3; i++) {
+                       mask[i] = col[i] * colfac;
+               }
        default:
                usage();
        } ARGEND
@@ -111,15 +99,18 @@ main(int argc, char *argv[])
                        return 1;
                }
                for (j = 0, k = 0; j < rowlen; j += 4, k += 3) {
-                       a = ntohs(row[j + 3]) / 65535.0f;
-                       rowout[k]     = ((ntohs(row[j]) * a)     + (mr * (1 - 
a))) / 257;
-                       rowout[k + 1] = ((ntohs(row[j + 1]) * a) + (mg * (1 - 
a))) / 257;
-                       rowout[k + 2] = ((ntohs(row[j + 2]) * a) + (mb * (1 - 
a))) / 257;
+                       a = ntohs(row[j + 3]);
+                       for (l = 0; l < 3; l++) {
+                               rowout[k + l] = (a * ntohs(row[j + l]) +
+                                                (65535 - a) * mask[l]) /
+                                               (257 * 65535);
+                       }
                }
                if (fwrite(rowout, 3, width, stdout) != width) {
                        fprintf(stderr, "%s: fwrite: %s\n", argv0, 
strerror(errno));
                        return 1;
                }
        }
+
        return 0;
 }