Correction to recent color balance compositor and sequencer changes.

- In my changes lift was acting like a second gamma.
- In blender 2.4x it was being added which gave ugly clipping.
- in Magic Bullet Looks it scales the color about 1.0: (col - 1 * (2-lift)) + 1

Did more testing and made sure the order of applying lift/gamma/gain works the same as MagicBulletLooks (tested on Collin's mac laptop).

2 files changed, 9 insertions, 8 deletions

diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index a4c1527c3c5..bd3e0129bcc 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -1494,7 +1494,7 @@ static StripColorBalance calc_cb(StripColorBalance * cb_)
 	int c;
 
 	for (c = 0; c < 3; c++) {
-		cb.lift[c] = 2.0f - pow(cb.lift[c], 2);
+		cb.lift[c] = 2.0f - cb.lift[c];
 	}
 
 	if(cb.flag & SEQ_COLOR_BALANCE_INVERSE_LIFT) {
@@ -1526,10 +1526,10 @@ static StripColorBalance calc_cb(StripColorBalance * cb_)
 	return cb;
 }
 
-/* pow(p[c] * cb.gain[c] + cb.lift[c], cb.gamma[c]) * mul;*/
-MINLINE float color_balance_fl(const float v, const float lift, const float gain, const float gamma, const float mul)
+/* note: lift is actually 2-lift */
+MINLINE float color_balance_fl(float v, const float lift, const float gain, const float gamma, const float mul)
 {
-	return powf(powf(v * gain, lift), gamma) * mul;
+	return powf((((v - 1.0f) * lift) + 1.0f) * gain, gamma) * mul;
 }
 
 static void make_cb_table_byte(float lift, float gain, float gamma,
diff --git a/source/blender/nodes/intern/CMP_nodes/CMP_colorbalance.c b/source/blender/nodes/intern/CMP_nodes/CMP_colorbalance.c
index f2e5815dfeb..cd614b12794 100644
--- a/source/blender/nodes/intern/CMP_nodes/CMP_colorbalance.c
+++ b/source/blender/nodes/intern/CMP_nodes/CMP_colorbalance.c
@@ -54,9 +54,10 @@ DO_INLINE float colorbalance_cdl(float in, float offset, float power, float slop
 	return powf(x, 1.f/power);
 }
 
-DO_INLINE float colorbalance_lgg(float in, float lift, float gamma, float gain)
-{
-	float x= powf(in * gain, lift);
+/* note: lift_lgg is just 2-lift */
+DO_INLINE float colorbalance_lgg(float in, float lift_lgg, float gamma, float gain)
+{	
+	float x= (((in - 1.0f) * lift_lgg) + 1.0f) * gain;
 
 	/* prevent NaN */
 	if (x < 0.f) x = 0.f;
@@ -124,7 +125,7 @@ static void node_composit_exec_colorbalance(void *data, bNode *node, bNodeStack
 		NodeColorBalance *n= (NodeColorBalance *)node->storage;
 		int c;
 		for (c = 0; c < 3; c++) {
-			n->lift_lgg[c] = 2.0f - pow(n->lift[c], 2);
+			n->lift_lgg[c] = 2.0f - n->lift[c];
 		}
 	}