Repeating SkBitmapProcState rounding bias

src/core/SkBitmapProcState_matrix_template.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmapProcState_MatrixTemplates_DEFINED
 #define SkBitmapProcState_MatrixTemplates_DEFINED
 
 #include "SkMath.h"
 #include "SkMathPriv.h"
 
 template <typename TileProc, bool tryDecal>
 void NoFilterProc_Scale(const SkBitmapProcState& s, uint32_t xy[],
                         int count, int x, int y) {
     SkASSERT((s.fInvType & ~(SkMatrix::kTranslate_Mask |
                              SkMatrix::kScale_Mask)) == 0);
 
     // we store y, x, x, x, x, x
 
     const unsigned maxX = s.fPixmap.width() - 1;
     SkFractionalInt fx;
     {
         SkPoint pt;
         s.fInvProc(s.fInvMatrix, SkIntToScalar(x) + SK_ScalarHalf,
                                   SkIntToScalar(y) + SK_ScalarHalf, &pt);
-        fx = SkScalarToFractionalInt(pt.fY);
+        fx = SkScalarToFractionalInt(pt.fY) + SkFixedToFractionalInt(s.fInvBiasY);
         const unsigned maxY = s.fPixmap.height() - 1;
         *xy++ = TileProc::Y(s, SkFractionalIntToFixed(fx), maxY);
-        fx = SkScalarToFractionalInt(pt.fX);
+        fx = SkScalarToFractionalInt(pt.fX) + SkFixedToFractionalInt(s.fInvBiasX);
     }
 
     if (0 == maxX) {
         // all of the following X values must be 0
         memset(xy, 0, count * sizeof(uint16_t));
         return;
     }
 
     const SkFractionalInt dx = s.fInvSxFractionalInt;
 
@@ skipping 36 matching lines @@
     SkASSERT(s.fInvType & SkMatrix::kAffine_Mask);
     SkASSERT((s.fInvType & ~(SkMatrix::kTranslate_Mask |
                              SkMatrix::kScale_Mask |
                              SkMatrix::kAffine_Mask)) == 0);
 
     SkPoint srcPt;
     s.fInvProc(s.fInvMatrix,
                SkIntToScalar(x) + SK_ScalarHalf,
                SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
 
-    SkFractionalInt fx = SkScalarToFractionalInt(srcPt.fX);
-    SkFractionalInt fy = SkScalarToFractionalInt(srcPt.fY);
+    SkFractionalInt fx = SkScalarToFractionalInt(srcPt.fX) + SkFixedToFractionalInt(s.fInvBiasX);
+    SkFractionalInt fy = SkScalarToFractionalInt(srcPt.fY) + SkFixedToFractionalInt(s.fInvBiasY);
     SkFractionalInt dx = s.fInvSxFractionalInt;
     SkFractionalInt dy = s.fInvKyFractionalInt;
     int maxX = s.fPixmap.width() - 1;
     int maxY = s.fPixmap.height() - 1;
 
     for (int i = count; i > 0; --i) {
         *xy++ = (TileProc::Y(s, SkFractionalIntToFixed(fy), maxY) << 16) |
                  TileProc::X(s, SkFractionalIntToFixed(fx), maxX);
         fx += dx; fy += dy;
     }
 }
 
 template <typename TileProc>
 void NoFilterProc_Persp(const SkBitmapProcState& s, uint32_t* SK_RESTRICT xy,
                         int count, int x, int y) {
     SkASSERT(s.fInvType & SkMatrix::kPerspective_Mask);
 
     int maxX = s.fPixmap.width() - 1;
     int maxY = s.fPixmap.height() - 1;
 
+    // TODO: inv bias support
     SkPerspIter   iter(s.fInvMatrix,
                        SkIntToScalar(x) + SK_ScalarHalf,
                        SkIntToScalar(y) + SK_ScalarHalf, count);
 
     while ((count = iter.next()) != 0) {
         const SkFixed* SK_RESTRICT srcXY = iter.getXY();
         while (--count >= 0) {
             *xy++ = (TileProc::Y(s, srcXY[1], maxY) << 16) |
                      TileProc::X(s, srcXY[0], maxX);
             srcXY += 2;
         }
     }
 }
 
 #endif