A bug fix.

Author: aous72

src/core/transform/ojph_colour_avx2.cpp

@@ -414,7 +414,7 @@ namespace ojph {
           __m256i u = _mm256_slli_epi32(t, shift);
           __m256 v = _mm256_cvtepi32_ps(u);
           v = _mm256_mul_ps(v, mul);
-          v = _mm256_add_ps(v, half);
+          v = _mm256_sub_ps(v, half);
           _mm256_storeu_ps(dp, v);
         }
       }

src/core/transform/ojph_colour_sse2.cpp

@@ -480,7 +480,7 @@ namespace ojph {
           __m128i u = _mm_slli_epi32(t, shift);
           __m128 v = _mm_cvtepi32_ps(u);
           v = _mm_mul_ps(v, mul);
-          v = _mm_add_ps(v, half);
+          v = _mm_sub_ps(v, half);
           _mm_storeu_ps(dp, v);
         }
       }

src/core/transform/ojph_colour_wasm.cpp

@@ -449,7 +449,7 @@ namespace ojph {
           v128_t u = wasm_i32x4_shl(t, shift);
           v128_t v = wasm_f32x4_convert_i32x4(u);
           v = wasm_f32x4_mul(v, mul);
-          v = wasm_f32x4_add(v, half);
+          v = wasm_f32x4_sub(v, half);
           wasm_v128_store(dp, v);
         }
       }