From 8065ec50f1937c1562810bfe2b216abfb98362b3 Mon Sep 17 00:00:00 2001 From: "commit-bot@chromium.org" Date: Tue, 11 Mar 2014 15:57:40 +0000 Subject: Add new module for distance field generation. This improves the speed over the previous method by 10x+, and makes using distance fields practical. BUG=skia:2173 Committed: http://code.google.com/p/skia/source/detail?r=13729 R=bsalomon@google.com, robertphillips@google.com Author: jvanverth@google.com Review URL: https://codereview.chromium.org/178543007 git-svn-id: http://skia.googlecode.com/svn/trunk@13740 2bbb7eff-a529-9590-31e7-b0007b416f81 --- src/core/SkDistanceFieldGen.cpp | 401 ++++++++++++++++++++++++++++++++++++++++ src/core/SkDistanceFieldGen.h | 25 +++ src/gpu/GrTextStrike.cpp | 108 ++++------- 3 files changed, 458 insertions(+), 76 deletions(-) create mode 100755 src/core/SkDistanceFieldGen.cpp create mode 100755 src/core/SkDistanceFieldGen.h (limited to 'src') diff --git a/src/core/SkDistanceFieldGen.cpp b/src/core/SkDistanceFieldGen.cpp new file mode 100755 index 0000000000..8370e0239c --- /dev/null +++ b/src/core/SkDistanceFieldGen.cpp @@ -0,0 +1,401 @@ +/* + * 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 +}; + +// We treat an "edge" as a place where we cross from a texel >= 128 to a texel < 128, +// or vice versa. This means we just need to check if the MSBs are different. +static bool found_edge(const unsigned char* imagePtr, int width) { + const int offsets[8] = {-1, 1, -width-1, -width, -width+1, width-1, width, width+1 }; + + // search for an edge + int checkVal = *imagePtr >> 7; + for (int i = 0; i < 8; ++i) { + const unsigned char* checkPtr = imagePtr + offsets[i]; + if (checkVal ^ (*checkPtr >> 7)) { + 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 + } + if (i > 0 && i < imageWidth-1 && j > 0 && j < imageHeight-1 && + found_edge(image, imageWidth)) { + *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; + } +} + +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); + } +} + +// 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) { + float dist; + if (currData->fAlpha > 0.5f) { + dist = -SkScalarSqrt(currData->fDistSq); + } else { + dist = SkScalarSqrt(currData->fDistSq); + } + + *dfPtr++ = pack_distance_field_val(dist, (float)distanceMagnitude); + ++currData; + ++currEdge; + } + currData += 2; + currEdge += 2; + } + + return true; +} diff --git a/src/core/SkDistanceFieldGen.h b/src/core/SkDistanceFieldGen.h new file mode 100755 index 0000000000..3d2ec23b75 --- /dev/null +++ b/src/core/SkDistanceFieldGen.h @@ -0,0 +1,25 @@ +/* + * Copyright 2014 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ +#ifndef SkDistanceFieldGen_DEFINED +#define SkDistanceFieldGen_DEFINED + +/** Given 8-bit mask data, generate the associated distance field + + * @param distanceField The distance field to be generated. Should already be allocated + * by the client with the padding below. + * @param image 8-bit mask we're using to generate the distance field. + * @param w Width of the image. + * @param h Height of the image. + * @param distanceMagnitude Largest possible absolute value for the distance. The distance field + * will be padded to w + 2*distanceMagnitude, h + 2*distanceMagnitude. + */ +bool SkGenerateDistanceFieldFromImage(unsigned char* distanceField, + const unsigned char* image, + int w, int h, + int distanceMagnitude); + +#endif diff --git a/src/gpu/GrTextStrike.cpp b/src/gpu/GrTextStrike.cpp index e303a23df8..0d7fcafe67 100644 --- a/src/gpu/GrTextStrike.cpp +++ b/src/gpu/GrTextStrike.cpp @@ -13,7 +13,7 @@ #include "SkString.h" #if SK_DISTANCEFIELD_FONTS -#include "edtaa3.h" +#include "SkDistanceFieldGen.h" #endif /////////////////////////////////////////////////////////////////////////////// @@ -199,8 +199,9 @@ void GrFontCache::dump() const { #endif #if SK_DISTANCEFIELD_FONTS -#define DISTANCE_FIELD_PAD 4 -#define DISTANCE_FIELD_RANGE (4.0) +// this acts as the max magnitude for the distance field, +// as well as the pad we need around the glyph +#define DISTANCE_FIELD_RANGE 4 #endif /* @@ -253,10 +254,10 @@ GrGlyph* GrTextStrike::generateGlyph(GrGlyph::PackedID packed, #if SK_DISTANCEFIELD_FONTS // expand bounds to hold full distance field data if (fUseDistanceField) { - bounds.fLeft -= DISTANCE_FIELD_PAD; - bounds.fRight += DISTANCE_FIELD_PAD; - bounds.fTop -= DISTANCE_FIELD_PAD; - bounds.fBottom += DISTANCE_FIELD_PAD; + bounds.fLeft -= DISTANCE_FIELD_RANGE; + bounds.fRight += DISTANCE_FIELD_RANGE; + bounds.fTop -= DISTANCE_FIELD_RANGE; + bounds.fBottom += DISTANCE_FIELD_RANGE; } #endif glyph->init(packed, bounds); @@ -294,15 +295,13 @@ bool GrTextStrike::addGlyphToAtlas(GrGlyph* glyph, GrFontScaler* scaler) { GrPlot* plot; #if SK_DISTANCEFIELD_FONTS if (fUseDistanceField) { - SkASSERT(1 == bytesPerPixel); - // we've already expanded the glyph dimensions to match the final size // but must shrink back down to get the packed glyph data int dfWidth = glyph->width(); int dfHeight = glyph->height(); - int width = dfWidth - 2*DISTANCE_FIELD_PAD; - int height = dfHeight - 2*DISTANCE_FIELD_PAD; - size_t stride = width*bytesPerPixel; + int width = dfWidth - 2*DISTANCE_FIELD_RANGE; + int height = dfHeight - 2*DISTANCE_FIELD_RANGE; + int stride = width*bytesPerPixel; size_t size = width * height * bytesPerPixel; SkAutoSMalloc<1024> storage(size); @@ -313,71 +312,28 @@ bool GrTextStrike::addGlyphToAtlas(GrGlyph* glyph, GrFontScaler* scaler) { // alloc storage for distance field glyph size_t dfSize = dfWidth * dfHeight * bytesPerPixel; SkAutoSMalloc<1024> dfStorage(dfSize); - - // copy glyph into distance field storage - sk_bzero(dfStorage.get(), dfSize); - - unsigned char* ptr = (unsigned char*) storage.get(); - unsigned char* dfPtr = (unsigned char*) dfStorage.get(); - size_t dfStride = dfWidth*bytesPerPixel; - dfPtr += DISTANCE_FIELD_PAD*dfStride; - dfPtr += DISTANCE_FIELD_PAD*bytesPerPixel; - - for (int i = 0; i < height; ++i) { - memcpy(dfPtr, ptr, stride); - - dfPtr += dfStride; - ptr += stride; - } - - // generate distance field data - SkAutoSMalloc<1024> distXStorage(dfWidth*dfHeight*sizeof(short)); - SkAutoSMalloc<1024> distYStorage(dfWidth*dfHeight*sizeof(short)); - SkAutoSMalloc<1024> outerDistStorage(dfWidth*dfHeight*sizeof(double)); - SkAutoSMalloc<1024> innerDistStorage(dfWidth*dfHeight*sizeof(double)); - SkAutoSMalloc<1024> gxStorage(dfWidth*dfHeight*sizeof(double)); - SkAutoSMalloc<1024> gyStorage(dfWidth*dfHeight*sizeof(double)); - - short* distX = (short*) distXStorage.get(); - short* distY = (short*) distYStorage.get(); - double* outerDist = (double*) outerDistStorage.get(); - double* innerDist = (double*) innerDistStorage.get(); - double* gx = (double*) gxStorage.get(); - double* gy = (double*) gyStorage.get(); - - dfPtr = (unsigned char*) dfStorage.get(); - EDTAA::computegradient(dfPtr, dfWidth, dfHeight, gx, gy); - EDTAA::edtaa3(dfPtr, gx, gy, dfWidth, dfHeight, distX, distY, outerDist); - - for (int i = 0; i < dfWidth*dfHeight; ++i) { - *dfPtr = 255 - *dfPtr; - dfPtr++; - } - dfPtr = (unsigned char*) dfStorage.get(); - sk_bzero(gx, sizeof(double)*dfWidth*dfHeight); - sk_bzero(gy, sizeof(double)*dfWidth*dfHeight); - EDTAA::computegradient(dfPtr, dfWidth, dfHeight, gx, gy); - EDTAA::edtaa3(dfPtr, gx, gy, dfWidth, dfHeight, distX, distY, innerDist); - - for (int i = 0; i < dfWidth*dfHeight; ++i) { - unsigned char val; - double outerval = outerDist[i]; - if (outerval < 0.0) { - outerval = 0.0; - } - double innerval = innerDist[i]; - if (innerval < 0.0) { - innerval = 0.0; - } - double dist = outerval - innerval; - if (dist <= -DISTANCE_FIELD_RANGE) { - val = 255; - } else if (dist > DISTANCE_FIELD_RANGE) { - val = 0; - } else { - val = (unsigned char)((DISTANCE_FIELD_RANGE-dist)*128.0/DISTANCE_FIELD_RANGE); + + if (1 == bytesPerPixel) { + (void) SkGenerateDistanceFieldFromImage((unsigned char*)dfStorage.get(), + (unsigned char*)storage.get(), + width, height, DISTANCE_FIELD_RANGE); + } else { + // TODO: Fix color emoji + // for now, copy glyph into distance field storage + // this is not correct, but it won't crash + sk_bzero(dfStorage.get(), dfSize); + unsigned char* ptr = (unsigned char*) storage.get(); + unsigned char* dfPtr = (unsigned char*) dfStorage.get(); + size_t dfStride = dfWidth*bytesPerPixel; + dfPtr += DISTANCE_FIELD_RANGE*dfStride; + dfPtr += DISTANCE_FIELD_RANGE*bytesPerPixel; + + for (int i = 0; i < height; ++i) { + memcpy(dfPtr, ptr, stride); + + dfPtr += dfStride; + ptr += stride; } - *dfPtr++ = val; } // copy to atlas -- cgit v1.2.3