Add "sharpen" option to SkSL, to LOD bias all textures

This adds a fixed bias (-0.5) to the computed LOD of all
mip-mapped texture fetches. (Technically, to all texture
fetches, but that only matters for mip-mapped ones).

Clients can opt-in with a new GrContextOption.

Bug: skia:7541
Bug: chromium:562162
Change-Id: Ie3cd0679c4ab66f62d2dc32e7e68e5c99355115e
Reviewed-on: https://skia-review.googlesource.com/106322
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/sksl/SkSLSPIRVCodeGenerator.cpp b/src/sksl/SkSLSPIRVCodeGenerator.cpp
index cb8b388521..d01a82dae2 100644
--- a/src/sksl/SkSLSPIRVCodeGenerator.cpp
+++ b/src/sksl/SkSLSPIRVCodeGenerator.cpp
@@ -824,8 +824,16 @@ SpvId SPIRVCodeGenerator::writeSpecialIntrinsic(const FunctionCall& c, SpecialIn
                                        out);
             } else {
                 ASSERT(c.fArguments.size() == 2);
-                this->writeInstruction(op, type, result, sampler, uv,
-                                       out);
+                if (fProgram.fSettings.fSharpenTextures) {
+                    FloatLiteral lodBias(fContext, -1, -0.5);
+                    this->writeInstruction(op, type, result, sampler, uv,
+                                           SpvImageOperandsBiasMask,
+                                           this->writeFloatLiteral(lodBias),
+                                           out);
+                } else {
+                    this->writeInstruction(op, type, result, sampler, uv,
+                                           out);
+                }
             }
             break;
         }