Update negative value handling on FETurbulence::CreateImageFilter

This CL updates how to handle negative values for baseFrequency
on <feTurbulence>. As the spec[1] says, it should leave it
unsupported, which means it's treated as if they hadn't been
specified when rendering.

[1]https://drafts.fxtf.org/filter-effects/#element-attrdef-feturbulence-basefrequency

Bug: 1068863
Change-Id: I6799cb26b6997f1b4d7afc9f5222a209064a30b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2141485Reviewed-by: Fredrik Söderquist <fs@opera.com>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Julie Kim <jkim@igalia.com>
Cr-Commit-Position: refs/heads/master@{#758465}

third_party/blink/renderer/platform/graphics/filters/fe_turbulence.cc

@@ -114,8 +114,14 @@ bool FETurbulence::SetStitchTiles(bool stitch) {
 }
 
 sk_sp<PaintFilter> FETurbulence::CreateImageFilter() {
-  if (base_frequency_x_ < 0 || base_frequency_y_ < 0)
-    return CreateTransparentBlack();
+  float base_frequency_x = base_frequency_x_;
+  float base_frequency_y = base_frequency_y_;
+  if (base_frequency_x < 0 || base_frequency_y < 0) {
+    // Negative values are unsupported which means it should be treated as
+    // if they hadn't been specified. So, it implies "0 0"(the initial
+    // value).
+    base_frequency_x = base_frequency_y = 0;
+  }
 
   PaintFilter::CropRect rect = GetCropRect();
   TurbulencePaintFilter::TurbulenceType type =
@@ -129,8 +135,8 @@ sk_sp<PaintFilter> FETurbulence::CreateImageFilter() {
   // and not the target bounding box scale (as SVGFilter::apply*Scale()
   // would do). Note also that we divide by the scale since this is
   // a frequency, not a period.
-  float base_frequency_x = base_frequency_x_ / GetFilter()->Scale();
-  float base_frequency_y = base_frequency_y_ / GetFilter()->Scale();
+  base_frequency_x /= GetFilter()->Scale();
+  base_frequency_y /= GetFilter()->Scale();
 
   // Cap the number of octaves to the maximum detectable when rendered with
   // 8 bits per pixel, plus one for higher bit depth.

third_party/blink/web_tests/css3/filters/effect-reference-turbulence-invalid.html

@@ -15,22 +15,32 @@
     <!-- type=fractalNoise -->
     <filter id="fn1" x="0" y="0" width="1" height="1">
         <feTurbulence type="fractalNoise" baseFrequency="-1 1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feComponentTransfer>
+            <feFuncR type="discrete" tableValues="1 0 1"/>
+            <feFuncG type="discrete" tableValues="0 0.502 0"/> <!-- map [0..1/3] -> 0; [1/3...2/3] -> 0.502; [2/3..1] -> 0 -->
+            <feFuncB type="discrete" tableValues="0"/>
+            <feFuncA type="discrete" tableValues="0 1 0"/>
+        </feComponentTransfer>
     </filter>
 
     <filter id="fn2" x="0" y="0" width="1" height="1">
         <feTurbulence type="fractalNoise" baseFrequency="1 -1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feComponentTransfer>
+            <feFuncR type="discrete" tableValues="1 0 1"/>
+            <feFuncG type="discrete" tableValues="0 0.502 0"/> <!-- map [0..1/3] -> 0; [1/3...2/3] -> 0.502; [2/3..1] -> 0 -->
+            <feFuncB type="discrete" tableValues="0"/>
+            <feFuncA type="discrete" tableValues="0 1 0"/>
+        </feComponentTransfer>
     </filter>
 
     <!-- type=turbulence -->
     <filter id="tb1" x="0" y="0" width="1" height="1">
-        <feTurbulence type="fractalNoise" baseFrequency="-1 1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feTurbulence type="turbulence" baseFrequency="-1 1"/>
+        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.502, 0 0 1 0 0, 0 0 0 1 1"/>
     </filter>
 
     <filter id="tb2" x="0" y="0" width="1" height="1">
-        <feTurbulence type="fractalNoise" baseFrequency="1 -1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feTurbulence type="turbulence" baseFrequency="1 -1"/>
+        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.502, 0 0 1 0 0, 0 0 0 1 1"/>
     </filter>
 </svg>

third_party/blink/web_tests/svg/filters/feTurbulence-negative-basefreq.html

@@ -3,26 +3,36 @@
     <!-- type=fractalNoise -->
     <filter id="fn1" x="0" y="0" width="1" height="1">
         <feTurbulence type="fractalNoise" baseFrequency="-1 1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feComponentTransfer>
+            <feFuncR type="discrete" tableValues="1 0 1"/>
+            <feFuncG type="discrete" tableValues="0 0.502 0"/> <!-- map [0..1/3] -> 0; [1/3...2/3] -> 0.502; [2/3..1] -> 0 -->
+            <feFuncB type="discrete" tableValues="0"/>
+            <feFuncA type="discrete" tableValues="0 1 0"/>
+        </feComponentTransfer>
     </filter>
     <rect width="100" height="100" filter="url(#fn1)"/>
 
     <filter id="fn2" x="0" y="0" width="1" height="1">
         <feTurbulence type="fractalNoise" baseFrequency="1 -1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feComponentTransfer>
+            <feFuncR type="discrete" tableValues="1 0 1"/>
+            <feFuncG type="discrete" tableValues="0 0.502 0"/> <!-- map [0..1/3] -> 0; [1/3...2/3] -> 0.502; [2/3..1] -> 0 -->
+            <feFuncB type="discrete" tableValues="0"/>
+            <feFuncA type="discrete" tableValues="0 1 0"/>
+        </feComponentTransfer>
     </filter>
     <rect width="100" height="100" filter="url(#fn2)" x="100"/>
 
     <!-- type=turbulence -->
     <filter id="tb1" x="0" y="0" width="1" height="1">
         <feTurbulence type="turbulence" baseFrequency="-1 1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.502, 0 0 1 0 0, 0 0 0 1 1"/>
     </filter>
     <rect width="100" height="100" filter="url(#tb1)" x="200"/>
 
     <filter id="tb2" x="0" y="0" width="1" height="1">
         <feTurbulence type="turbulence" baseFrequency="1 -1"/>
-        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.5, 0 0 1 0 0, 0 0 0 1 1"/>
+        <feColorMatrix values="1 0 0 0 0, 0 1 0 0 0.502, 0 0 1 0 0, 0 0 0 1 1"/>
     </filter>
     <rect width="100" height="100" filter="url(#tb2)" x="300"/>
 </svg>