The Tor Browser: gfx/skia/trunk/src/core/SkDistanceFieldGen.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkDistanceFieldGen.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkDistanceFieldGen.cpp

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rwxr-xr-x

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkDistanceFieldGen.h"
 #include "SkPoint.h"
 struct DFData {
     float   fAlpha;      // alpha value of source texel
     float   fDistSq;     // distance squared to nearest (so far) edge texel
     SkPoint fDistVector; // distance vector to nearest (so far) edge texel
 };
 enum NeighborFlags {
     kLeft_NeighborFlag        = 0x01,
     kRight_NeighborFlag       = 0x02,
     kTopLeft_NeighborFlag     = 0x04,
     kTop_NeighborFlag         = 0x08,
     kTopRight_NeighborFlag    = 0x10,
     kBottomLeft_NeighborFlag  = 0x20,
     kBottom_NeighborFlag      = 0x40,
     kBottomRight_NeighborFlag = 0x80,
     kAll_NeighborFlags        = 0xff,
     kNeighborFlagCount        = 8
 };
 // We treat an "edge" as a place where we cross from black to non-black, or vice versa.
 // 'neighborFlags' is used to limit the directions in which we test to avoid indexing
 // outside of the image
 static bool found_edge(const unsigned char* imagePtr, int width, int neighborFlags) {
     // the order of these should match the neighbor flags above
     const int kNum8ConnectedNeighbors = 8;
     const int offsets[8] = {-1, 1, -width-1, -width, -width+1, width-1, width, width+1 };
     SkASSERT(kNum8ConnectedNeighbors == kNeighborFlagCount);
     // search for an edge
     bool currVal = (*imagePtr != 0);
     for (int i = 0; i < kNum8ConnectedNeighbors; ++i) {
         bool checkVal;
         if ((1 << i) & neighborFlags) {
             const unsigned char* checkPtr = imagePtr + offsets[i];
             checkVal = (*checkPtr != 0);
         } else {
             checkVal = false;
         }
         SkASSERT(checkVal == 0 || checkVal == 1);
         SkASSERT(currVal == 0 || currVal == 1);
         if (checkVal != currVal) {
             return true;
         }
     }
     return false;
 }
 static void init_glyph_data(DFData* data, unsigned char* edges, const unsigned char* image,
                             int dataWidth, int dataHeight,
                             int imageWidth, int imageHeight,
                             int pad) {
     data += pad*dataWidth;
     data += pad;
     edges += (pad*dataWidth + pad);
     for (int j = 0; j < imageHeight; ++j) {
         for (int i = 0; i < imageWidth; ++i) {
             if (255 == *image) {
                 data->fAlpha = 1.0f;
             } else {
                 data->fAlpha = (*image)*0.00392156862f;  // 1/255
             }
             int checkMask = kAll_NeighborFlags;
             if (i == 0) {
                 checkMask &= ~(kLeft_NeighborFlag|kTopLeft_NeighborFlag|kBottomLeft_NeighborFlag);
             }
             if (i == imageWidth-1) {
                 checkMask &= ~(kRight_NeighborFlag|kTopRight_NeighborFlag|kBottomRight_NeighborFlag);
             }
             if (j == 0) {
                 checkMask &= ~(kTopLeft_NeighborFlag|kTop_NeighborFlag|kTopRight_NeighborFlag);
             }
             if (j == imageHeight-1) {
                 checkMask &= ~(kBottomLeft_NeighborFlag|kBottom_NeighborFlag|kBottomRight_NeighborFlag);
             }
             if (found_edge(image, imageWidth, checkMask)) {
                 *edges = 255;  // using 255 makes for convenient debug rendering
             }
             ++data;
             ++image;
             ++edges;
         }
         data += 2*pad;
         edges += 2*pad;
     }
 }
 // from Gustavson (2011)
 // computes the distance to an edge given an edge normal vector and a pixel's alpha value
 // assumes that direction has been pre-normalized
 static float edge_distance(const SkPoint& direction, float alpha) {
     float dx = direction.fX;
     float dy = direction.fY;
     float distance;
     if (SkScalarNearlyZero(dx) || SkScalarNearlyZero(dy)) {
         distance = 0.5f - alpha;
     } else {
         // this is easier if we treat the direction as being in the first octant
         // (other octants are symmetrical)
         dx = SkScalarAbs(dx);
         dy = SkScalarAbs(dy);
         if (dx < dy) {
             SkTSwap(dx, dy);
         }
         // a1 = 0.5*dy/dx is the smaller fractional area chopped off by the edge
         // to avoid the divide, we just consider the numerator
         float a1num = 0.5f*dy;
         // we now compute the approximate distance, depending where the alpha falls
         // relative to the edge fractional area
         // if 0 <= alpha < a1
         if (alpha*dx < a1num) {
             // TODO: find a way to do this without square roots?
             distance = 0.5f*(dx + dy) - SkScalarSqrt(2.0f*dx*dy*alpha);
         // if a1 <= alpha <= 1 - a1
         } else if (alpha*dx < (dx - a1num)) {
             distance = (0.5f - alpha)*dx;
         // if 1 - a1 < alpha <= 1
         } else {
             // TODO: find a way to do this without square roots?
             distance = -0.5f*(dx + dy) + SkScalarSqrt(2.0f*dx*dy*(1.0f - alpha));
         }
     }
     return distance;
 }
 static void init_distances(DFData* data, unsigned char* edges, int width, int height) {
     // skip one pixel border
     DFData* currData = data;
     DFData* prevData = data - width;
     DFData* nextData = data + width;
     for (int j = 0; j < height; ++j) {
         for (int i = 0; i < width; ++i) {
             if (*edges) {
                 // we should not be in the one-pixel outside band
                 SkASSERT(i > 0 && i < width-1 && j > 0 && j < height-1);
                 // gradient will point from low to high
                 // +y is down in this case
                 // i.e., if you're outside, gradient points towards edge
                 // if you're inside, gradient points away from edge
                 SkPoint currGrad;
                 currGrad.fX = (prevData+1)->fAlpha - (prevData-1)->fAlpha
                              + SK_ScalarSqrt2*(currData+1)->fAlpha
                              - SK_ScalarSqrt2*(currData-1)->fAlpha
                              + (nextData+1)->fAlpha - (nextData-1)->fAlpha;
                 currGrad.fY = (nextData-1)->fAlpha - (prevData-1)->fAlpha
                              + SK_ScalarSqrt2*nextData->fAlpha
                              - SK_ScalarSqrt2*prevData->fAlpha
                              + (nextData+1)->fAlpha - (prevData+1)->fAlpha;
                 currGrad.setLengthFast(1.0f);
                 // init squared distance to edge and distance vector
                 float dist = edge_distance(currGrad, currData->fAlpha);
                 currGrad.scale(dist, &currData->fDistVector);
                 currData->fDistSq = dist*dist;
             } else {
                 // init distance to "far away"
                 currData->fDistSq = 2000000.f;
                 currData->fDistVector.fX = 1000.f;
                 currData->fDistVector.fY = 1000.f;
             }
             ++currData;
             ++prevData;
             ++nextData;
             ++edges;
         }
     }
 }
 // Danielsson's 8SSEDT
 // first stage forward pass
 // (forward in Y, forward in X)
 static void F1(DFData* curr, int width) {
     // upper left
     DFData* check = curr - width-1;
     SkPoint distVec = check->fDistVector;
     float distSq = check->fDistSq - 2.0f*(distVec.fX + distVec.fY - 1.0f);
     if (distSq < curr->fDistSq) {
         distVec.fX -= 1.0f;
         distVec.fY -= 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // up
     check = curr - width;
     distVec = check->fDistVector;
     distSq = check->fDistSq - 2.0f*distVec.fY + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fY -= 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // upper right
     check = curr - width+1;
     distVec = check->fDistVector;
     distSq = check->fDistSq + 2.0f*(distVec.fX - distVec.fY + 1.0f);
     if (distSq < curr->fDistSq) {
         distVec.fX += 1.0f;
         distVec.fY -= 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // left
     check = curr - 1;
     distVec = check->fDistVector;
     distSq = check->fDistSq - 2.0f*distVec.fX + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fX -= 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
 }
 // second stage forward pass
 // (forward in Y, backward in X)
 static void F2(DFData* curr, int width) {
     // right
     DFData* check = curr + 1;
     float distSq = check->fDistSq;
     SkPoint distVec = check->fDistVector;
     distSq = check->fDistSq + 2.0f*distVec.fX + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fX += 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
 }
 // first stage backward pass
 // (backward in Y, forward in X)
 static void B1(DFData* curr, int width) {
     // left
     DFData* check = curr - 1;
     SkPoint distVec = check->fDistVector;
     float distSq = check->fDistSq - 2.0f*distVec.fX + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fX -= 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
 }
 // second stage backward pass
 // (backward in Y, backwards in X)
 static void B2(DFData* curr, int width) {
     // right
     DFData* check = curr + 1;
     SkPoint distVec = check->fDistVector;
     float distSq = check->fDistSq + 2.0f*distVec.fX + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fX += 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // bottom left
     check = curr + width-1;
     distVec = check->fDistVector;
     distSq = check->fDistSq - 2.0f*(distVec.fX - distVec.fY - 1.0f);
     if (distSq < curr->fDistSq) {
         distVec.fX -= 1.0f;
         distVec.fY += 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // bottom
     check = curr + width;
     distVec = check->fDistVector;
     distSq = check->fDistSq + 2.0f*distVec.fY + 1.0f;
     if (distSq < curr->fDistSq) {
         distVec.fY += 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
     // bottom right
     check = curr + width+1;
     distVec = check->fDistVector;
     distSq = check->fDistSq + 2.0f*(distVec.fX + distVec.fY + 1.0f);
     if (distSq < curr->fDistSq) {
         distVec.fX += 1.0f;
         distVec.fY += 1.0f;
         curr->fDistSq = distSq;
         curr->fDistVector = distVec;
     }
 }
 // enable this to output edge data rather than the distance field
 #define DUMP_EDGE 0
 #if !DUMP_EDGE
 static unsigned char pack_distance_field_val(float dist, float distanceMagnitude) {
     if (dist <= -distanceMagnitude) {
         return 255;
     } else if (dist > distanceMagnitude) {
         return 0;
     } else {
         return (unsigned char)((distanceMagnitude-dist)*128.0f/distanceMagnitude);
     }
 }
 #endif
 // assumes an 8-bit image and distance field
 bool SkGenerateDistanceFieldFromImage(unsigned char* distanceField,
                                       const unsigned char* image,
                                       int width, int height,
                                       int distanceMagnitude) {
     SkASSERT(NULL != distanceField);
     SkASSERT(NULL != image);
     // the final distance field will have additional texels on each side to handle
     // the maximum distance
     // we expand our temp data by one more on each side to simplify
     // the scanning code -- will always be treated as infinitely far away
     int pad = distanceMagnitude+1;
     // set params for distance field data
     int dataWidth = width + 2*pad;
     int dataHeight = height + 2*pad;
     // create temp data
     size_t dataSize = dataWidth*dataHeight*sizeof(DFData);
     SkAutoSMalloc<1024> dfStorage(dataSize);
     DFData* dataPtr = (DFData*) dfStorage.get();
     sk_bzero(dataPtr, dataSize);
     SkAutoSMalloc<1024> edgeStorage(dataWidth*dataHeight*sizeof(char));
     unsigned char* edgePtr = (unsigned char*) edgeStorage.get();
     sk_bzero(edgePtr, dataWidth*dataHeight*sizeof(char));
     // copy glyph into distance field storage
     init_glyph_data(dataPtr, edgePtr, image,
                     dataWidth, dataHeight,
                     width, height, pad);
     // create initial distance data, particularly at edges
     init_distances(dataPtr, edgePtr, dataWidth, dataHeight);
     // now perform Euclidean distance transform to propagate distances
     // forwards in y
     DFData* currData = dataPtr+dataWidth+1; // skip outer buffer
     unsigned char* currEdge = edgePtr+dataWidth+1;
     for (int j = 1; j < dataHeight-1; ++j) {
         // forwards in x
         for (int i = 1; i < dataWidth-1; ++i) {
             // don't need to calculate distance for edge pixels
             if (!*currEdge) {
                 F1(currData, dataWidth);
             }
             ++currData;
             ++currEdge;
         }
         // backwards in x
         --currData; // reset to end
         --currEdge;
         for (int i = 1; i < dataWidth-1; ++i) {
             // don't need to calculate distance for edge pixels
             if (!*currEdge) {
                 F2(currData, dataWidth);
             }
             --currData;
             --currEdge;
         }
         currData += dataWidth+1;
         currEdge += dataWidth+1;
     }
     // backwards in y
     currData = dataPtr+dataWidth*(dataHeight-2) - 1; // skip outer buffer
     currEdge = edgePtr+dataWidth*(dataHeight-2) - 1;
     for (int j = 1; j < dataHeight-1; ++j) {
         // forwards in x
         for (int i = 1; i < dataWidth-1; ++i) {
             // don't need to calculate distance for edge pixels
             if (!*currEdge) {
                 B1(currData, dataWidth);
             }
             ++currData;
             ++currEdge;
         }
         // backwards in x
         --currData; // reset to end
         --currEdge;
         for (int i = 1; i < dataWidth-1; ++i) {
             // don't need to calculate distance for edge pixels
             if (!*currEdge) {
                 B2(currData, dataWidth);
             }
             --currData;
             --currEdge;
         }
         currData -= dataWidth-1;
         currEdge -= dataWidth-1;
     }
     // copy results to final distance field data
     currData = dataPtr + dataWidth+1;
     currEdge = edgePtr + dataWidth+1;
     unsigned char *dfPtr = distanceField;
     for (int j = 1; j < dataHeight-1; ++j) {
         for (int i = 1; i < dataWidth-1; ++i) {
 #if DUMP_EDGE
             unsigned char val = sk_float_round2int(255*currData->fAlpha);
             if (*currEdge) {
                 val = 128;
             }
             *dfPtr++ = val;
 #else
             float dist;
             if (currData->fAlpha > 0.5f) {
                 dist = -SkScalarSqrt(currData->fDistSq);
             } else {
                 dist = SkScalarSqrt(currData->fDistSq);
             }
             *dfPtr++ = pack_distance_field_val(dist, (float)distanceMagnitude);
 #endif
             ++currData;
             ++currEdge;
         }
         currData += 2;
         currEdge += 2;
     }
     return true;
 }

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gfx/skia/trunk/src/core/SkDistanceFieldGen.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkDistanceFieldGen.cpp