change default filtering parameters:

* type is now 'strong'
  * strength is now '60'

These help with gradients and blocking

Change-Id: Ie1c8265c557306ef5e9ccefacf43e10946e55370

NEWS

@@ -1,6 +1,7 @@
 - next version:
   * WebPINewRGB/WebPINewYUVA accept being passed a NULL output buffer
     and will perform auto-allocation.
+  * default filter option is now '-strong -f 60'
 
 - 10/30/12: version 0.2.1
   * Various security related fixes

README

@@ -151,7 +151,8 @@ options:
   -sns <int> ............. Spatial Noise Shaping (0:off, 100:max)
   -f <int> ............... filter strength (0=off..100)
   -sharpness <int> ....... filter sharpness (0:most .. 7:least sharp)
-  -strong ................ use strong filter instead of simple.
+  -strong ................ use strong filter instead of simple (default).
+  -nostrong .............. use simple filter instead of strong.
   -partition_limit <int> . limit quality to fit the 512k limit on
                            the first partition (0=no degradation ... 100=full)
   -pass <int> ............ analysis pass number (1..10)
@@ -211,8 +212,8 @@ Namely:
      in-loop processing. The higher the value, the smoother the
      highly-compressed area will look. This is particularly useful when aiming
      at very small files. Typical values are around 20-30. Note that using the
-     option -strong will change the type of filtering. Use "-f 0" to turn
-     filtering off.
+     option -strong/-nostrong will change the type of filtering. Use "-f 0" to
+     turn filtering off.
   * 'm' controls the trade-off between encoding speed and quality. Default is 4.
      You can try -m 5 or -m 6 to explore more (time-consuming) encoding
      possibilities. A lower value will result in faster encoding at the expense

examples/cwebp.c

@@ -537,7 +537,9 @@ static void HelpLong(void) {
   printf("  -f <int> ............... filter strength (0=off..100)\n");
   printf("  -sharpness <int> ....... "
          "filter sharpness (0:most .. 7:least sharp)\n");
-  printf("  -strong ................ use strong filter instead of simple.\n");
+  printf("  -strong ................ use strong filter instead "
+                                     "of simple (default).\n");
+  printf("  -nostrong .............. use simple filter instead of strong.\n");
   printf("  -partition_limit <int> . limit quality to fit the 512k limit on\n");
   printf("                           "
          "the first partition (0=no degradation ... 100=full)\n");
@@ -724,6 +726,8 @@ int main(int argc, const char *argv[]) {
       config.emulate_jpeg_size = 1;
     } else if (!strcmp(argv[c], "-strong")) {
       config.filter_type = 1;
+    } else if (!strcmp(argv[c], "-nostrong")) {
+      config.filter_type = 0;
     } else if (!strcmp(argv[c], "-sharpness") && c < argc - 1) {
       config.filter_sharpness = strtol(argv[++c], NULL, 0);
     } else if (!strcmp(argv[c], "-pass") && c < argc - 1) {

man/cwebp.1

@@ -1,5 +1,5 @@
 .\"                                      Hey, EMACS: -*- nroff -*-
-.TH CWEBP 1 "February 6, 2013"
+.TH CWEBP 1 "February 15, 2013"
 .SH NAME
 cwebp \- compress an image file to a WebP file
 .SH SYNOPSIS
@@ -94,8 +94,12 @@ Specify the sharpness of the filtering (if used).
 Range is 0 (sharpest) to 7 (least sharp). Default is 0.
 .TP
 .B \-strong
-Use a stronger filtering than the default one (if filtering is being
-used thanks to the \fB\-f\fP option). Strong filtering is off by default.
+Use strong filtering (if filtering is being used thanks to the
+\fB\-f\fP option). Strong filtering is on by default.
+.TP
+.B \-nostrong
+Disable strong filtering (if filtering is being used thanks to the
+\fB\-f\fP option) and use simple filtering instead.
 .TP
 .BI \-segments " int
 Change the number of partitions to use during the segmentation of the
@@ -224,7 +228,7 @@ cwebp \-q 50 -lossless picture.png \-o picture_lossless.webp
 .br
 cwebp \-q 70 picture_with_alpha.png \-o picture_with_alpha.webp
 .br
-cwebp \-sns 70 \-f 50 \-strong \-af \-size 60000 picture.png \-o picture.webp
+cwebp \-sns 70 \-f 50 \-size 60000 picture.png \-o picture.webp
 
 .SH AUTHORS
 \fBcwebp\fP was written by the WebP team.

src/enc/config.c

@@ -31,9 +31,9 @@ int WebPConfigInitInternal(WebPConfig* config,
   config->target_PSNR = 0.;
   config->method = 4;
   config->sns_strength = 50;
-  config->filter_strength = 20;   // default: light filtering
+  config->filter_strength = 60;   // rather high filtering, helps w/ gradients.
   config->filter_sharpness = 0;
-  config->filter_type = 0;        // default: simple
+  config->filter_type = 1;        // default: strong (so U/V is filtered too)
   config->partitions = 0;
   config->segments = 4;
   config->pass = 1;