Composite Filter: Handle negative K's in Arithmetic mode.

(bzr r3839)

3 files changed, 19 insertions, 4 deletions

diff --git a/src/display/nr-filter-composite.cpp b/src/display/nr-filter-composite.cpp
index a5b1d5297..29207b6b9 100644
--- a/src/display/nr-filter-composite.cpp
+++ b/src/display/nr-filter-composite.cpp
@@ -73,13 +73,13 @@ static int arith_k1, arith_k2, arith_k3, arith_k4;
 inline void
 composite_arithmetic(unsigned char *r, unsigned char const *a, unsigned char const *b)
 {
-    r[0] = NR::clamp(NR_NORMALIZE_31(arith_k1 * a[0] * b[0]
+    r[0] = NR_NORMALIZE_31(NR::clamp3(arith_k1 * a[0] * b[0]
                  + arith_k2 * a[0] + arith_k3 * b[0] + arith_k4));
-    r[1] = NR::clamp(NR_NORMALIZE_31(arith_k1 * a[1] * b[1]
+    r[1] = NR_NORMALIZE_31(NR::clamp3(arith_k1 * a[1] * b[1]
                  + arith_k2 * a[1] + arith_k3 * b[1] + arith_k4));
-    r[2] = NR::clamp(NR_NORMALIZE_31(arith_k1 * a[2] * b[2]
+    r[2] = NR_NORMALIZE_31(NR::clamp3(arith_k1 * a[2] * b[2]
                  + arith_k2 * a[2] + arith_k3 * b[2] + arith_k4));
-    r[3] = NR::clamp(NR_NORMALIZE_31(arith_k1 * a[3] * b[3]
+    r[3] = NR_NORMALIZE_31(NR::clamp3(arith_k1 * a[3] * b[3]
                  + arith_k2 * a[3] + arith_k3 * b[3] + arith_k4));
 }
 
diff --git a/src/display/nr-filter-utils.cpp b/src/display/nr-filter-utils.cpp
index 52c8ecc7d..ddd41298c 100644
--- a/src/display/nr-filter-utils.cpp
+++ b/src/display/nr-filter-utils.cpp
@@ -8,6 +8,12 @@ int clamp(int const val) {
     return val;
 }
 
+int clamp3(int const val) {
+    if (val < 0) return 0;
+    if (val > 16581375) return 16581375;
+    return val;
+}
+
 int clamp_alpha(int const val, int const alpha) {
     if (val < 0) return 0;
     if (val > alpha) return alpha;
diff --git a/src/display/nr-filter-utils.h b/src/display/nr-filter-utils.h
index 5ac6fa5ab..91c295e94 100644
--- a/src/display/nr-filter-utils.h
+++ b/src/display/nr-filter-utils.h
@@ -14,6 +14,7 @@
 
 #include "round.h"
 
+/* Shouldn't these be inlined? */
 namespace NR {
 
 /**
@@ -26,6 +27,14 @@ namespace NR {
 int clamp(int const val);
 
 /**
+ * Clamps an integer value to a value between 0 and 255^3.
+ *
+ * \return 0 if the value is smaller than 0, 255^3 (16581375) if it is greater than 255^3, else v
+ * \param v the value to clamp
+ */
+int clamp3(int const val);
+
+/**
  * Macro to use the clamp function with double inputs and unsigned char output
  */
 #define CLAMP_D_TO_U8(v) (unsigned char) clamp((int)round((v)))