diff --git a/src/dsp/filters.c b/src/dsp/filters.c
index c9232ff1..bb779b39 100644
--- a/src/dsp/filters.c
+++ b/src/dsp/filters.c
@@ -32,13 +32,9 @@
 
 #if !WEBP_NEON_OMIT_C_CODE
 static WEBP_INLINE void PredictLine_C(const uint8_t* src, const uint8_t* pred,
-                                      uint8_t* dst, int length, int inverse) {
+                                      uint8_t* dst, int length) {
   int i;
-  if (inverse) {
-    for (i = 0; i < length; ++i) dst[i] = (uint8_t)(src[i] + pred[i]);
-  } else {
-    for (i = 0; i < length; ++i) dst[i] = (uint8_t)(src[i] - pred[i]);
-  }
+  for (i = 0; i < length; ++i) dst[i] = (uint8_t)(src[i] - pred[i]);
 }
 
 //------------------------------------------------------------------------------
@@ -47,19 +43,19 @@ static WEBP_INLINE void PredictLine_C(const uint8_t* src, const uint8_t* pred,
 static WEBP_INLINE void DoHorizontalFilter_C(const uint8_t* in,
                                              int width, int height, int stride,
                                              int row, int num_rows,
-                                             int inverse, uint8_t* out) {
+                                             uint8_t* out) {
   const uint8_t* preds;
   const size_t start_offset = row * stride;
   const int last_row = row + num_rows;
   DCHECK(in, out);
   in += start_offset;
   out += start_offset;
-  preds = inverse ? out : in;
+  preds = in;
 
   if (row == 0) {
     // Leftmost pixel is the same as input for topmost scanline.
     out[0] = in[0];
-    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
+    PredictLine_C(in + 1, preds, out + 1, width - 1);
     row = 1;
     preds += stride;
     in += stride;
@@ -69,8 +65,8 @@ static WEBP_INLINE void DoHorizontalFilter_C(const uint8_t* in,
   // Filter line-by-line.
   while (row < last_row) {
     // Leftmost pixel is predicted from above.
-    PredictLine_C(in, preds - stride, out, 1, inverse);
-    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
+    PredictLine_C(in, preds - stride, out, 1);
+    PredictLine_C(in + 1, preds, out + 1, width - 1);
     ++row;
     preds += stride;
     in += stride;
@@ -84,20 +80,20 @@ static WEBP_INLINE void DoHorizontalFilter_C(const uint8_t* in,
 static WEBP_INLINE void DoVerticalFilter_C(const uint8_t* in,
                                            int width, int height, int stride,
                                            int row, int num_rows,
-                                           int inverse, uint8_t* out) {
+                                           uint8_t* out) {
   const uint8_t* preds;
   const size_t start_offset = row * stride;
   const int last_row = row + num_rows;
   DCHECK(in, out);
   in += start_offset;
   out += start_offset;
-  preds = inverse ? out : in;
+  preds = in;
 
   if (row == 0) {
     // Very first top-left pixel is copied.
     out[0] = in[0];
     // Rest of top scan-line is left-predicted.
-    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
+    PredictLine_C(in + 1, preds, out + 1, width - 1);
     row = 1;
     in += stride;
     out += stride;
@@ -108,7 +104,7 @@ static WEBP_INLINE void DoVerticalFilter_C(const uint8_t* in,
 
   // Filter line-by-line.
   while (row < last_row) {
-    PredictLine_C(in, preds, out, width, inverse);
+    PredictLine_C(in, preds, out, width);
     ++row;
     preds += stride;
     in += stride;
@@ -129,19 +125,19 @@ static WEBP_INLINE int GradientPredictor_C(uint8_t a, uint8_t b, uint8_t c) {
 static WEBP_INLINE void DoGradientFilter_C(const uint8_t* in,
                                            int width, int height, int stride,
                                            int row, int num_rows,
-                                           int inverse, uint8_t* out) {
+                                           uint8_t* out) {
   const uint8_t* preds;
   const size_t start_offset = row * stride;
   const int last_row = row + num_rows;
   DCHECK(in, out);
   in += start_offset;
   out += start_offset;
-  preds = inverse ? out : in;
+  preds = in;
 
   // left prediction for top scan-line
   if (row == 0) {
     out[0] = in[0];
-    PredictLine_C(in + 1, preds, out + 1, width - 1, inverse);
+    PredictLine_C(in + 1, preds, out + 1, width - 1);
     row = 1;
     preds += stride;
     in += stride;
@@ -152,12 +148,12 @@ static WEBP_INLINE void DoGradientFilter_C(const uint8_t* in,
   while (row < last_row) {
     int w;
     // leftmost pixel: predict from above.
-    PredictLine_C(in, preds - stride, out, 1, inverse);
+    PredictLine_C(in, preds - stride, out, 1);
     for (w = 1; w < width; ++w) {
       const int pred = GradientPredictor_C(preds[w - 1],
                                            preds[w - stride],
                                            preds[w - stride - 1]);
-      out[w] = (uint8_t)(in[w] + (inverse ? pred : -pred));
+      out[w] = (uint8_t)(in[w] - pred);
     }
     ++row;
     preds += stride;
@@ -174,18 +170,17 @@ static WEBP_INLINE void DoGradientFilter_C(const uint8_t* in,
 #if !WEBP_NEON_OMIT_C_CODE
 static void HorizontalFilter_C(const uint8_t* data, int width, int height,
                                int stride, uint8_t* filtered_data) {
-  DoHorizontalFilter_C(data, width, height, stride, 0, height, 0,
-                       filtered_data);
+  DoHorizontalFilter_C(data, width, height, stride, 0, height, filtered_data);
 }
 
 static void VerticalFilter_C(const uint8_t* data, int width, int height,
                              int stride, uint8_t* filtered_data) {
-  DoVerticalFilter_C(data, width, height, stride, 0, height, 0, filtered_data);
+  DoVerticalFilter_C(data, width, height, stride, 0, height, filtered_data);
 }
 
 static void GradientFilter_C(const uint8_t* data, int width, int height,
                              int stride, uint8_t* filtered_data) {
-  DoGradientFilter_C(data, width, height, stride, 0, height, 0, filtered_data);
+  DoGradientFilter_C(data, width, height, stride, 0, height, filtered_data);
 }
 #endif  // !WEBP_NEON_OMIT_C_CODE