path: root/src/ports/SkFontHost_FreeType_common.cpp

/*
 * Copyright 2006-2012 The Android Open Source Project
 * Copyright 2012 Mozilla Foundation
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkBitmap.h"
#include "SkCanvas.h"
#include "SkColor.h"
#include "SkColorData.h"
#include "SkFDot6.h"
#include "SkFontHost_FreeType_common.h"
#include "SkPath.h"
#include "SkTo.h"

#include <utility>

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_BITMAP_H
#include FT_IMAGE_H
#include FT_OUTLINE_H
// In the past, FT_GlyphSlot_Own_Bitmap was defined in this header file.
#include FT_SYNTHESIS_H

// FT_LOAD_COLOR and the corresponding FT_Pixel_Mode::FT_PIXEL_MODE_BGRA
// were introduced in FreeType 2.5.0.
// The following may be removed once FreeType 2.5.0 is required to build.
#ifndef FT_LOAD_COLOR
#    define FT_LOAD_COLOR ( 1L << 20 )
#    define FT_PIXEL_MODE_BGRA 7
#endif

//#define SK_SHOW_TEXT_BLIT_COVERAGE

#ifdef SK_DEBUG
const char* SkTraceFtrGetError(int e) {
    switch ((FT_Error)e) {
        #undef FTERRORS_H_
        #define FT_ERRORDEF( e, v, s ) case v: return s;
        #define FT_ERROR_START_LIST
        #define FT_ERROR_END_LIST
        #include FT_ERRORS_H
        #undef FT_ERRORDEF
        #undef FT_ERROR_START_LIST
        #undef FT_ERROR_END_LIST
        default: return "";
    }
}
#endif  // SK_DEBUG

namespace {

FT_Pixel_Mode compute_pixel_mode(SkMask::Format format) {
    switch (format) {
        case SkMask::kBW_Format:
            return FT_PIXEL_MODE_MONO;
        case SkMask::kA8_Format:
        default:
            return FT_PIXEL_MODE_GRAY;
    }
}

///////////////////////////////////////////////////////////////////////////////

uint16_t packTriple(U8CPU r, U8CPU g, U8CPU b) {
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
    r = SkTMax(r, (U8CPU)0x40);
    g = SkTMax(g, (U8CPU)0x40);
    b = SkTMax(b, (U8CPU)0x40);
#endif
    return SkPack888ToRGB16(r, g, b);
}

uint16_t grayToRGB16(U8CPU gray) {
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
    gray = SkTMax(gray, (U8CPU)0x40);
#endif
    return SkPack888ToRGB16(gray, gray, gray);
}

int bittst(const uint8_t data[], int bitOffset) {
    SkASSERT(bitOffset >= 0);
    int lowBit = data[bitOffset >> 3] >> (~bitOffset & 7);
    return lowBit & 1;
}

/**
 *  Copies a FT_Bitmap into an SkMask with the same dimensions.
 *
 *  FT_PIXEL_MODE_MONO
 *  FT_PIXEL_MODE_GRAY
 *  FT_PIXEL_MODE_LCD
 *  FT_PIXEL_MODE_LCD_V
 */
template<bool APPLY_PREBLEND>
void copyFT2LCD16(const FT_Bitmap& bitmap, const SkMask& mask, int lcdIsBGR,
                  const uint8_t* tableR, const uint8_t* tableG, const uint8_t* tableB)
{
    SkASSERT(SkMask::kLCD16_Format == mask.fFormat);
    if (FT_PIXEL_MODE_LCD != bitmap.pixel_mode) {
        SkASSERT(mask.fBounds.width() == static_cast<int>(bitmap.width));
    }
    if (FT_PIXEL_MODE_LCD_V != bitmap.pixel_mode) {
        SkASSERT(mask.fBounds.height() == static_cast<int>(bitmap.rows));
    }

    const uint8_t* src = bitmap.buffer;
    uint16_t* dst = reinterpret_cast<uint16_t*>(mask.fImage);
    const size_t dstRB = mask.fRowBytes;

    const int width = mask.fBounds.width();
    const int height = mask.fBounds.height();

    switch (bitmap.pixel_mode) {
        case FT_PIXEL_MODE_MONO:
            for (int y = height; y --> 0;) {
                for (int x = 0; x < width; ++x) {
                    dst[x] = -bittst(src, x);
                }
                dst = (uint16_t*)((char*)dst + dstRB);
                src += bitmap.pitch;
            }
            break;
        case FT_PIXEL_MODE_GRAY:
            for (int y = height; y --> 0;) {
                for (int x = 0; x < width; ++x) {
                    dst[x] = grayToRGB16(src[x]);
                }
                dst = (uint16_t*)((char*)dst + dstRB);
                src += bitmap.pitch;
            }
            break;
        case FT_PIXEL_MODE_LCD:
            SkASSERT(3 * mask.fBounds.width() == static_cast<int>(bitmap.width));
            for (int y = height; y --> 0;) {
                const uint8_t* triple = src;
                if (lcdIsBGR) {
                    for (int x = 0; x < width; x++) {
                        dst[x] = packTriple(sk_apply_lut_if<APPLY_PREBLEND>(triple[2], tableR),
                                            sk_apply_lut_if<APPLY_PREBLEND>(triple[1], tableG),
                                            sk_apply_lut_if<APPLY_PREBLEND>(triple[0], tableB));
                        triple += 3;
                    }
                } else {
                    for (int x = 0; x < width; x++) {
                        dst[x] = packTriple(sk_apply_lut_if<APPLY_PREBLEND>(triple[0], tableR),
                                            sk_apply_lut_if<APPLY_PREBLEND>(triple[1], tableG),
                                            sk_apply_lut_if<APPLY_PREBLEND>(triple[2], tableB));
                        triple += 3;
                    }
                }
                src += bitmap.pitch;
                dst = (uint16_t*)((char*)dst + dstRB);
            }
            break;
        case FT_PIXEL_MODE_LCD_V:
            SkASSERT(3 * mask.fBounds.height() == static_cast<int>(bitmap.rows));
            for (int y = height; y --> 0;) {
                const uint8_t* srcR = src;
                const uint8_t* srcG = srcR + bitmap.pitch;
                const uint8_t* srcB = srcG + bitmap.pitch;
                if (lcdIsBGR) {
                    using std::swap;
                    swap(srcR, srcB);
                }
                for (int x = 0; x < width; x++) {
                    dst[x] = packTriple(sk_apply_lut_if<APPLY_PREBLEND>(*srcR++, tableR),
                                        sk_apply_lut_if<APPLY_PREBLEND>(*srcG++, tableG),
                                        sk_apply_lut_if<APPLY_PREBLEND>(*srcB++, tableB));
                }
                src += 3 * bitmap.pitch;
                dst = (uint16_t*)((char*)dst + dstRB);
            }
            break;
        default:
            SkDEBUGF("FT_Pixel_Mode %d", bitmap.pixel_mode);
            SkDEBUGFAIL("unsupported FT_Pixel_Mode for LCD16");
            break;
    }
}

/**
 *  Copies a FT_Bitmap into an SkMask with the same dimensions.
 *
 *  Yes, No, Never Requested, Never Produced
 *
 *                        kBW kA8 k3D kARGB32 kLCD16
 *  FT_PIXEL_MODE_MONO     Y   Y  NR     N       Y
 *  FT_PIXEL_MODE_GRAY     N   Y  NR     N       Y
 *  FT_PIXEL_MODE_GRAY2   NP  NP  NR    NP      NP
 *  FT_PIXEL_MODE_GRAY4   NP  NP  NR    NP      NP
 *  FT_PIXEL_MODE_LCD     NP  NP  NR    NP      NP
 *  FT_PIXEL_MODE_LCD_V   NP  NP  NR    NP      NP
 *  FT_PIXEL_MODE_BGRA     N   N  NR     Y       N
 *
 *  TODO: All of these N need to be Y or otherwise ruled out.
 */
void copyFTBitmap(const FT_Bitmap& srcFTBitmap, SkMask& dstMask) {
    SkASSERTF(dstMask.fBounds.width() == static_cast<int>(srcFTBitmap.width),
              "dstMask.fBounds.width() = %d\n"
              "static_cast<int>(srcFTBitmap.width) = %d",
              dstMask.fBounds.width(),
              static_cast<int>(srcFTBitmap.width)
    );
    SkASSERTF(dstMask.fBounds.height() == static_cast<int>(srcFTBitmap.rows),
              "dstMask.fBounds.height() = %d\n"
              "static_cast<int>(srcFTBitmap.rows) = %d",
              dstMask.fBounds.height(),
              static_cast<int>(srcFTBitmap.rows)
    );

    const uint8_t* src = reinterpret_cast<const uint8_t*>(srcFTBitmap.buffer);
    const FT_Pixel_Mode srcFormat = static_cast<FT_Pixel_Mode>(srcFTBitmap.pixel_mode);
    // FT_Bitmap::pitch is an int and allowed to be negative.
    const int srcPitch = srcFTBitmap.pitch;
    const size_t srcRowBytes = SkTAbs(srcPitch);

    uint8_t* dst = dstMask.fImage;
    const SkMask::Format dstFormat = static_cast<SkMask::Format>(dstMask.fFormat);
    const size_t dstRowBytes = dstMask.fRowBytes;

    const size_t width = srcFTBitmap.width;
    const size_t height = srcFTBitmap.rows;

    if (SkMask::kLCD16_Format == dstFormat) {
        copyFT2LCD16<false>(srcFTBitmap, dstMask, false, nullptr, nullptr, nullptr);
        return;
    }

    if ((FT_PIXEL_MODE_MONO == srcFormat && SkMask::kBW_Format == dstFormat) ||
        (FT_PIXEL_MODE_GRAY == srcFormat && SkMask::kA8_Format == dstFormat))
    {
        size_t commonRowBytes = SkTMin(srcRowBytes, dstRowBytes);
        for (size_t y = height; y --> 0;) {
            memcpy(dst, src, commonRowBytes);
            src += srcPitch;
            dst += dstRowBytes;
        }
    } else if (FT_PIXEL_MODE_MONO == srcFormat && SkMask::kA8_Format == dstFormat) {
        for (size_t y = height; y --> 0;) {
            uint8_t byte = 0;
            int bits = 0;
            const uint8_t* src_row = src;
            uint8_t* dst_row = dst;
            for (size_t x = width; x --> 0;) {
                if (0 == bits) {
                    byte = *src_row++;
                    bits = 8;
                }
                *dst_row++ = byte & 0x80 ? 0xff : 0x00;
                bits--;
                byte <<= 1;
            }
            src += srcPitch;
            dst += dstRowBytes;
        }
    } else if (FT_PIXEL_MODE_BGRA == srcFormat && SkMask::kARGB32_Format == dstFormat) {
        // FT_PIXEL_MODE_BGRA is pre-multiplied.
        for (size_t y = height; y --> 0;) {
            const uint8_t* src_row = src;
            SkPMColor* dst_row = reinterpret_cast<SkPMColor*>(dst);
            for (size_t x = 0; x < width; ++x) {
                uint8_t b = *src_row++;
                uint8_t g = *src_row++;
                uint8_t r = *src_row++;
                uint8_t a = *src_row++;
                *dst_row++ = SkPackARGB32(a, r, g, b);
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
                *(dst_row-1) = SkFourByteInterp256(*(dst_row-1), SK_ColorWHITE, 0x40);
#endif
            }
            src += srcPitch;
            dst += dstRowBytes;
        }
    } else {
        SkDEBUGF("FT_Pixel_Mode %d, SkMask::Format %d\n", srcFormat, dstFormat);
        SkDEBUGFAIL("unsupported combination of FT_Pixel_Mode and SkMask::Format");
    }
}

inline int convert_8_to_1(unsigned byte) {
    SkASSERT(byte <= 0xFF);
    // Arbitrary decision that making the cutoff at 1/4 instead of 1/2 in general looks better.
    return (byte >> 6) != 0;
}

uint8_t pack_8_to_1(const uint8_t alpha[8]) {
    unsigned bits = 0;
    for (int i = 0; i < 8; ++i) {
        bits <<= 1;
        bits |= convert_8_to_1(alpha[i]);
    }
    return SkToU8(bits);
}

void packA8ToA1(const SkMask& mask, const uint8_t* src, size_t srcRB) {
    const int height = mask.fBounds.height();
    const int width = mask.fBounds.width();
    const int octs = width >> 3;
    const int leftOverBits = width & 7;

    uint8_t* dst = mask.fImage;
    const int dstPad = mask.fRowBytes - SkAlign8(width)/8;
    SkASSERT(dstPad >= 0);

    const int srcPad = srcRB - width;
    SkASSERT(srcPad >= 0);

    for (int y = 0; y < height; ++y) {
        for (int i = 0; i < octs; ++i) {
            *dst++ = pack_8_to_1(src);
            src += 8;
        }
        if (leftOverBits > 0) {
            unsigned bits = 0;
            int shift = 7;
            for (int i = 0; i < leftOverBits; ++i, --shift) {
                bits |= convert_8_to_1(*src++) << shift;
            }
            *dst++ = bits;
        }
        src += srcPad;
        dst += dstPad;
    }
}

inline SkMask::Format SkMaskFormat_for_SkColorType(SkColorType colorType) {
    switch (colorType) {
        case kAlpha_8_SkColorType:
            return SkMask::kA8_Format;
        case kN32_SkColorType:
            return SkMask::kARGB32_Format;
        default:
            SkDEBUGFAIL("unsupported SkBitmap::Config");
            return SkMask::kA8_Format;
    }
}

inline SkColorType SkColorType_for_FTPixelMode(FT_Pixel_Mode pixel_mode) {
    switch (pixel_mode) {
        case FT_PIXEL_MODE_MONO:
        case FT_PIXEL_MODE_GRAY:
            return kAlpha_8_SkColorType;
        case FT_PIXEL_MODE_BGRA:
            return kN32_SkColorType;
        default:
            SkDEBUGFAIL("unsupported FT_PIXEL_MODE");
            return kAlpha_8_SkColorType;
    }
}

inline SkColorType SkColorType_for_SkMaskFormat(SkMask::Format format) {
    switch (format) {
        case SkMask::kBW_Format:
        case SkMask::kA8_Format:
        case SkMask::kLCD16_Format:
            return kAlpha_8_SkColorType;
        case SkMask::kARGB32_Format:
            return kN32_SkColorType;
        default:
            SkDEBUGFAIL("unsupported destination SkBitmap::Config");
            return kAlpha_8_SkColorType;
    }
}

}  // namespace

void SkScalerContext_FreeType_Base::generateGlyphImage(
    FT_Face face,
    const SkGlyph& glyph,
    const SkMatrix& bitmapTransform)
{
    const bool doBGR = SkToBool(fRec.fFlags & SkScalerContext::kLCD_BGROrder_Flag);
    const bool doVert = SkToBool(fRec.fFlags & SkScalerContext::kLCD_Vertical_Flag);

    switch ( face->glyph->format ) {
        case FT_GLYPH_FORMAT_OUTLINE: {
            FT_Outline* outline = &face->glyph->outline;

            int dx = 0, dy = 0;
            if (fRec.fFlags & SkScalerContext::kSubpixelPositioning_Flag) {
                dx = SkFixedToFDot6(glyph.getSubXFixed());
                dy = SkFixedToFDot6(glyph.getSubYFixed());
                // negate dy since freetype-y-goes-up and skia-y-goes-down
                dy = -dy;
            }

            memset(glyph.fImage, 0, glyph.rowBytes() * glyph.fHeight);

            if (SkMask::kLCD16_Format == glyph.fMaskFormat) {
                FT_Outline_Translate(outline, dx, dy);
                FT_Error err = FT_Render_Glyph(face->glyph, doVert ? FT_RENDER_MODE_LCD_V :
                                                                     FT_RENDER_MODE_LCD);
                if (err) {
                    SK_TRACEFTR(err, "Could not render glyph %x.", face->glyph);
                    return;
                }

                SkMask mask;
                glyph.toMask(&mask);
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
                memset(mask.fImage, 0x80, mask.fBounds.height() * mask.fRowBytes);
#endif
                FT_GlyphSlotRec& ftGlyph = *face->glyph;

                if (!SkIRect::Intersects(mask.fBounds,
                                         SkIRect::MakeXYWH( ftGlyph.bitmap_left,
                                                           -ftGlyph.bitmap_top,
                                                            ftGlyph.bitmap.width,
                                                            ftGlyph.bitmap.rows)))
                {
                    return;
                }

                // If the FT_Bitmap extent is larger, discard bits of the bitmap outside the mask.
                // If the SkMask extent is larger, shrink mask to fit bitmap (clearing discarded).
                unsigned char* origBuffer = ftGlyph.bitmap.buffer;
                // First align the top left (origin).
                if (-ftGlyph.bitmap_top < mask.fBounds.fTop) {
                    int32_t topDiff = mask.fBounds.fTop - (-ftGlyph.bitmap_top);
                    ftGlyph.bitmap.buffer += ftGlyph.bitmap.pitch * topDiff;
                    ftGlyph.bitmap.rows -= topDiff;
                    ftGlyph.bitmap_top = -mask.fBounds.fTop;
                }
                if (ftGlyph.bitmap_left < mask.fBounds.fLeft) {
                    int32_t leftDiff = mask.fBounds.fLeft - ftGlyph.bitmap_left;
                    ftGlyph.bitmap.buffer += leftDiff;
                    ftGlyph.bitmap.width -= leftDiff;
                    ftGlyph.bitmap_left = mask.fBounds.fLeft;
                }
                if (mask.fBounds.fTop < -ftGlyph.bitmap_top) {
                    mask.fImage += mask.fRowBytes * (-ftGlyph.bitmap_top - mask.fBounds.fTop);
                    mask.fBounds.fTop = -ftGlyph.bitmap_top;
                }
                if (mask.fBounds.fLeft < ftGlyph.bitmap_left) {
                    mask.fImage += sizeof(uint16_t) * (ftGlyph.bitmap_left - mask.fBounds.fLeft);
                    mask.fBounds.fLeft = ftGlyph.bitmap_left;
                }
                // Origins aligned, clean up the width and height.
                int ftVertScale = (doVert ? 3 : 1);
                int ftHoriScale = (doVert ? 1 : 3);
                if (mask.fBounds.height() * ftVertScale < SkToInt(ftGlyph.bitmap.rows)) {
                    ftGlyph.bitmap.rows = mask.fBounds.height() * ftVertScale;
                }
                if (mask.fBounds.width() * ftHoriScale < SkToInt(ftGlyph.bitmap.width)) {
                    ftGlyph.bitmap.width = mask.fBounds.width() * ftHoriScale;
                }
                if (SkToInt(ftGlyph.bitmap.rows) < mask.fBounds.height() * ftVertScale) {
                    mask.fBounds.fBottom = mask.fBounds.fTop + ftGlyph.bitmap.rows / ftVertScale;
                }
                if (SkToInt(ftGlyph.bitmap.width) < mask.fBounds.width() * ftHoriScale) {
                    mask.fBounds.fRight = mask.fBounds.fLeft + ftGlyph.bitmap.width / ftHoriScale;
                }
                if (fPreBlend.isApplicable()) {
                    copyFT2LCD16<true>(ftGlyph.bitmap, mask, doBGR,
                                       fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
                } else {
                    copyFT2LCD16<false>(ftGlyph.bitmap, mask, doBGR,
                                        fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
                }
                // Restore the buffer pointer so FreeType can properly free it.
                ftGlyph.bitmap.buffer = origBuffer;
            } else {
                FT_BBox     bbox;
                FT_Bitmap   target;
                FT_Outline_Get_CBox(outline, &bbox);
                /*
                    what we really want to do for subpixel is
                        offset(dx, dy)
                        compute_bounds
                        offset(bbox & !63)
                    but that is two calls to offset, so we do the following, which
                    achieves the same thing with only one offset call.
                */
                FT_Outline_Translate(outline, dx - ((bbox.xMin + dx) & ~63),
                                              dy - ((bbox.yMin + dy) & ~63));

                target.width = glyph.fWidth;
                target.rows = glyph.fHeight;
                target.pitch = glyph.rowBytes();
                target.buffer = reinterpret_cast<uint8_t*>(glyph.fImage);
                target.pixel_mode = compute_pixel_mode( (SkMask::Format)fRec.fMaskFormat);
                target.num_grays = 256;

                FT_Outline_Get_Bitmap(face->glyph->library, outline, &target);
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
                for (int y = 0; y < glyph.fHeight; ++y) {
                    for (int x = 0; x < glyph.fWidth; ++x) {
                        uint8_t& a = ((uint8_t*)glyph.fImage)[(glyph.rowBytes() * y) + x];
                        a = SkTMax<uint8_t>(a, 0x20);
                    }
                }
#endif
            }
        } break;

        case FT_GLYPH_FORMAT_BITMAP: {
            FT_Pixel_Mode pixel_mode = static_cast<FT_Pixel_Mode>(face->glyph->bitmap.pixel_mode);
            SkMask::Format maskFormat = static_cast<SkMask::Format>(glyph.fMaskFormat);

            // Assume that the other formats do not exist.
            SkASSERT(FT_PIXEL_MODE_MONO == pixel_mode ||
                     FT_PIXEL_MODE_GRAY == pixel_mode ||
                     FT_PIXEL_MODE_BGRA == pixel_mode);

            // These are the only formats this ScalerContext should request.
            SkASSERT(SkMask::kBW_Format == maskFormat ||
                     SkMask::kA8_Format == maskFormat ||
                     SkMask::kARGB32_Format == maskFormat ||
                     SkMask::kLCD16_Format == maskFormat);

            // If no scaling needed, directly copy glyph bitmap.
            if (bitmapTransform.isIdentity()) {
                SkMask dstMask;
                glyph.toMask(&dstMask);
                copyFTBitmap(face->glyph->bitmap, dstMask);
                break;
            }

            // Otherwise, scale the bitmap.

            // Copy the FT_Bitmap into an SkBitmap (either A8 or ARGB)
            SkBitmap unscaledBitmap;
            // TODO: mark this as sRGB when the blits will be sRGB.
            unscaledBitmap.allocPixels(SkImageInfo::Make(face->glyph->bitmap.width,
                                                         face->glyph->bitmap.rows,
                                                         SkColorType_for_FTPixelMode(pixel_mode),
                                                         kPremul_SkAlphaType));

            SkMask unscaledBitmapAlias;
            unscaledBitmapAlias.fImage = reinterpret_cast<uint8_t*>(unscaledBitmap.getPixels());
            unscaledBitmapAlias.fBounds.set(0, 0, unscaledBitmap.width(), unscaledBitmap.height());
            unscaledBitmapAlias.fRowBytes = unscaledBitmap.rowBytes();
            unscaledBitmapAlias.fFormat = SkMaskFormat_for_SkColorType(unscaledBitmap.colorType());
            copyFTBitmap(face->glyph->bitmap, unscaledBitmapAlias);

            // Wrap the glyph's mask in a bitmap, unless the glyph's mask is BW or LCD.
            // BW requires an A8 target for resizing, which can then be down sampled.
            // LCD should use a 4x A8 target, which will then be down sampled.
            // For simplicity, LCD uses A8 and is replicated.
            int bitmapRowBytes = 0;
            if (SkMask::kBW_Format != maskFormat && SkMask::kLCD16_Format != maskFormat) {
                bitmapRowBytes = glyph.rowBytes();
            }
            SkBitmap dstBitmap;
            // TODO: mark this as sRGB when the blits will be sRGB.
            dstBitmap.setInfo(SkImageInfo::Make(glyph.fWidth, glyph.fHeight,
                                                SkColorType_for_SkMaskFormat(maskFormat),
                                                kPremul_SkAlphaType),
                              bitmapRowBytes);
            if (SkMask::kBW_Format == maskFormat || SkMask::kLCD16_Format == maskFormat) {
                dstBitmap.allocPixels();
            } else {
                dstBitmap.setPixels(glyph.fImage);
            }

            // Scale unscaledBitmap into dstBitmap.
            SkCanvas canvas(dstBitmap);
#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
            canvas.clear(0x33FF0000);
#else
            canvas.clear(SK_ColorTRANSPARENT);
#endif
            canvas.translate(-glyph.fLeft, -glyph.fTop);
            canvas.concat(bitmapTransform);
            canvas.translate(face->glyph->bitmap_left, -face->glyph->bitmap_top);

            SkPaint paint;
            // Using kMedium FilterQuality will cause mipmaps to be generated. Use
            // kLow when the results will be roughly the same in order to avoid
            // the mipmap generation cost.
            // See skbug.com/6967
            if (bitmapTransform.getMinScale() < 0.5) {
                paint.setFilterQuality(kMedium_SkFilterQuality);
            } else {
                paint.setFilterQuality(kLow_SkFilterQuality);
            }
            canvas.drawBitmap(unscaledBitmap, 0, 0, &paint);

            // If the destination is BW or LCD, convert from A8.
            if (SkMask::kBW_Format == maskFormat) {
                // Copy the A8 dstBitmap into the A1 glyph.fImage.
                SkMask dstMask;
                glyph.toMask(&dstMask);
                packA8ToA1(dstMask, dstBitmap.getAddr8(0, 0), dstBitmap.rowBytes());
            } else if (SkMask::kLCD16_Format == maskFormat) {
                // Copy the A8 dstBitmap into the LCD16 glyph.fImage.
                uint8_t* src = dstBitmap.getAddr8(0, 0);
                uint16_t* dst = reinterpret_cast<uint16_t*>(glyph.fImage);
                for (int y = dstBitmap.height(); y --> 0;) {
                    for (int x = 0; x < dstBitmap.width(); ++x) {
                        dst[x] = grayToRGB16(src[x]);
                    }
                    dst = (uint16_t*)((char*)dst + glyph.rowBytes());
                    src += dstBitmap.rowBytes();
                }
            }

        } break;

        default:
            SkDEBUGFAIL("unknown glyph format");
            memset(glyph.fImage, 0, glyph.rowBytes() * glyph.fHeight);
            return;
    }

// We used to always do this pre-USE_COLOR_LUMINANCE, but with colorlum,
// it is optional
#if defined(SK_GAMMA_APPLY_TO_A8)
    if (SkMask::kA8_Format == glyph.fMaskFormat && fPreBlend.isApplicable()) {
        uint8_t* SK_RESTRICT dst = (uint8_t*)glyph.fImage;
        unsigned rowBytes = glyph.rowBytes();

        for (int y = glyph.fHeight - 1; y >= 0; --y) {
            for (int x = glyph.fWidth - 1; x >= 0; --x) {
                dst[x] = fPreBlend.fG[dst[x]];
            }
            dst += rowBytes;
        }
    }
#endif
}

///////////////////////////////////////////////////////////////////////////////

namespace {

int move_proc(const FT_Vector* pt, void* ctx) {
    SkPath* path = (SkPath*)ctx;
    path->close();  // to close the previous contour (if any)
    path->moveTo(SkFDot6ToScalar(pt->x), -SkFDot6ToScalar(pt->y));
    return 0;
}

int line_proc(const FT_Vector* pt, void* ctx) {
    SkPath* path = (SkPath*)ctx;
    path->lineTo(SkFDot6ToScalar(pt->x), -SkFDot6ToScalar(pt->y));
    return 0;
}

int quad_proc(const FT_Vector* pt0, const FT_Vector* pt1, void* ctx) {
    SkPath* path = (SkPath*)ctx;
    path->quadTo(SkFDot6ToScalar(pt0->x), -SkFDot6ToScalar(pt0->y),
                 SkFDot6ToScalar(pt1->x), -SkFDot6ToScalar(pt1->y));
    return 0;
}

int cubic_proc(const FT_Vector* pt0, const FT_Vector* pt1, const FT_Vector* pt2, void* ctx) {
    SkPath* path = (SkPath*)ctx;
    path->cubicTo(SkFDot6ToScalar(pt0->x), -SkFDot6ToScalar(pt0->y),
                  SkFDot6ToScalar(pt1->x), -SkFDot6ToScalar(pt1->y),
                  SkFDot6ToScalar(pt2->x), -SkFDot6ToScalar(pt2->y));
    return 0;
}

}  // namespace

bool SkScalerContext_FreeType_Base::generateGlyphPath(FT_Face face, SkPath* path) {
    FT_Outline_Funcs    funcs;

    funcs.move_to   = move_proc;
    funcs.line_to   = line_proc;
    funcs.conic_to  = quad_proc;
    funcs.cubic_to  = cubic_proc;
    funcs.shift     = 0;
    funcs.delta     = 0;

    FT_Error err = FT_Outline_Decompose(&face->glyph->outline, &funcs, path);

    if (err != 0) {
        path->reset();
        return false;
    }

    path->close();
    return true;
}