Replace interp() with clut_{3,4}D stages.

I tried to follow exactly the same strategy as a start.
(Though I did fix the off-by-one dimensions.)

It does rather look like we only need 3D and 4D now
that I've looked at the call sites.

Looks like about a 20% speedup.

Change-Id: I8b1af64750ad1750716ee1ab0767e64591c7206a
Reviewed-on: https://skia-review.googlesource.com/32842
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

1 files changed, 0 insertions, 56 deletions

diff --git a/src/core/SkColorLookUpTable.cpp b/src/core/SkColorLookUpTable.cpp
index c558afb0e1..f376621e7f 100644
--- a/src/core/SkColorLookUpTable.cpp
+++ b/src/core/SkColorLookUpTable.cpp
@@ -18,59 +18,3 @@ SkColorLookUpTable::SkColorLookUpTable(uint8_t inputChannels, const uint8_t limi
         SkASSERT(fLimits[i] > 1);
     }
 }
-
-// Our general strategy is to recursively interpolate each dimension,
-// accumulating the index to sample at, and our current pixel stride to help accumulate the index.
-template <int dim>
-static Sk4f interp_dimension(const float* table, const uint8_t* limits,
-                             const float* src, int index, int stride) {
-    // We'd logically like to sample this dimension at x.
-    int limit = limits[dim];
-    float x = src[dim] * (limit - 1);
-
-    // We can't index an array by a float (darn) so we have to snap to nearby integers lo and hi.
-    int lo = (int)(x          ),
-        hi = (int)(x + 0.9999f);
-
-    // Recursively sample at lo and hi.
-    Sk4f L = interp_dimension<dim-1>(table,limits,src, stride*lo + index, stride*limit),
-         H = interp_dimension<dim-1>(table,limits,src, stride*hi + index, stride*limit);
-
-    // Linearly interpolate those colors based on their distance to x.
-    float t = (x - lo);
-    return (1 - t)*L + t*H;
-}
-
-// Bottom out our recursion at 0 dimensions, i.e. just return the color at index.
-template <>
-Sk4f interp_dimension<-1>(const float* table, const uint8_t* limits,
-                          const float* src, int index, int stride) {
-    return {
-        table[3*index+0],
-        table[3*index+1],
-        table[3*index+2],
-        0.0f,
-    };
-}
-
-template <int dim>
-static Sk4f interp_dimension(const float* table, const uint8_t* limits, const float* src) {
-    // Start our accumulated index and stride off at their identity values, 0 and 1.
-    return interp_dimension<dim>(table, limits, src, 0,1);
-}
-
-void SkColorLookUpTable::interp(float* dst, const float* src) const {
-    Sk4f rgb;
-    switch (fInputChannels-1) {
-        case 0: rgb = interp_dimension<0>(this->table(), fLimits, src); break;
-        case 1: rgb = interp_dimension<1>(this->table(), fLimits, src); break;
-        case 2: rgb = interp_dimension<2>(this->table(), fLimits, src); break;
-        case 3: rgb = interp_dimension<3>(this->table(), fLimits, src); break;
-        default: SkDEBUGFAIL("oops"); return;
-    }
-
-    rgb = Sk4f::Max(0, Sk4f::Min(rgb, 1));
-    dst[0] = rgb[0];
-    dst[1] = rgb[1];
-    dst[2] = rgb[2];
-}