Cache glyph mask images.
benchmark old ns/op new ns/op delta BenchmarkDrawString-4 88103151 14188817 -83.90%
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Nigel Tao
parent
62e59645ee
commit
fe26067669
1 changed files with 139 additions and 29 deletions
168
truetype/face.go
168
truetype/face.go
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@ -13,6 +13,10 @@ import (
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"golang.org/x/image/math/fixed"
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)
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func powerOf2(i int) bool {
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return i != 0 && (i&(i-1)) == 0
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}
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// Options are optional arguments to NewFace.
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type Options struct {
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// Size is the font size in points, as in "a 10 point font size".
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@ -30,6 +34,14 @@ type Options struct {
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// A zero value means to use no hinting.
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Hinting font.Hinting
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// GlyphCacheEntries is the number of entries in the glyph mask image
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// cache.
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//
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// If non-zero, it must be a power of 2.
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//
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// A zero value means to use 512 entries.
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GlyphCacheEntries int
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// SubPixelsX is the number of sub-pixel locations a glyph's dot is
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// quantized to, in the horizontal direction. For example, a value of 8
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// means that the dot is quantized to 1/8th of a pixel. This quantization
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@ -37,7 +49,7 @@ type Options struct {
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// width. A higher value gives a more faithful glyph image, but reduces the
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// effectiveness of the glyph cache.
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//
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// It must be a power of 2, and be between 1 and 64 inclusive.
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// If non-zero, it must be a power of 2, and be between 1 and 64 inclusive.
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//
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// A zero value means to use 4 sub-pixel locations.
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SubPixelsX int
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@ -49,7 +61,7 @@ type Options struct {
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// width. A higher value gives a more faithful glyph image, but reduces the
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// effectiveness of the glyph cache.
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//
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// It must be a power of 2, and be between 1 and 64 inclusive.
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// If non-zero, it must be a power of 2, and be between 1 and 64 inclusive.
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//
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// A zero value means to use 1 sub-pixel location.
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SubPixelsY int
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@ -80,7 +92,16 @@ func (o *Options) hinting() font.Hinting {
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return font.HintingNone
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}
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func (o *Options) subPixelsX() (halfQuantum, mask fixed.Int26_6) {
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func (o *Options) glyphCacheEntries() int {
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if o != nil && powerOf2(o.GlyphCacheEntries) {
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return o.GlyphCacheEntries
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}
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// 512 is 128 * 4 * 1, which lets us cache 128 glyphs at 4 * 1 subpixel
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// locations in the X and Y direction.
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return 512
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}
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func (o *Options) subPixelsX() (value uint32, halfQuantum, mask fixed.Int26_6) {
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if o != nil {
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switch o.SubPixelsX {
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case 1, 2, 4, 8, 16, 32, 64:
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@ -93,7 +114,7 @@ func (o *Options) subPixelsX() (halfQuantum, mask fixed.Int26_6) {
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return subPixels(4)
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}
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func (o *Options) subPixelsY() (halfQuantum, mask fixed.Int26_6) {
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func (o *Options) subPixelsY() (value uint32, halfQuantum, mask fixed.Int26_6) {
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if o != nil {
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switch o.SubPixelsX {
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case 1, 2, 4, 8, 16, 32, 64:
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@ -107,8 +128,8 @@ func (o *Options) subPixelsY() (halfQuantum, mask fixed.Int26_6) {
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return subPixels(1)
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}
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// subPixels returns the bias and mask that leads to q quantized sub-pixel
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// locations per full pixel.
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// subPixels returns q and the bias and mask that leads to q quantized
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// sub-pixel locations per full pixel.
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//
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// For example, q == 4 leads to a bias of 8 and a mask of 0xfffffff0, or -16,
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// because we want to round fractions of fixed.Int26_6 as:
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@ -126,8 +147,26 @@ func (o *Options) subPixelsY() (halfQuantum, mask fixed.Int26_6) {
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// ...
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// When q == 64, we want bias == 0 and mask == -1. (The no-op case).
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// The pattern is clear.
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func subPixels(q int) (bias, mask fixed.Int26_6) {
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return 32 / fixed.Int26_6(q), -64 / fixed.Int26_6(q)
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func subPixels(q int) (value uint32, bias, mask fixed.Int26_6) {
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return uint32(q), 32 / fixed.Int26_6(q), -64 / fixed.Int26_6(q)
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}
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// cacheEntry caches the arguments and return values of rasterize.
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type cacheEntry struct {
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key cacheKey
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val cacheVal
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}
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type cacheKey struct {
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index Index
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fx, fy uint8
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}
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type cacheVal struct {
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advanceWidth fixed.Int26_6
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offset image.Point
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gw int
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gh int
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}
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// NewFace returns a new font.Face for the given Font.
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@ -136,9 +175,16 @@ func NewFace(f *Font, opts *Options) font.Face {
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f: f,
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hinting: opts.hinting(),
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scale: fixed.Int26_6(0.5 + (opts.size() * opts.dpi() * 64 / 72)),
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cache: make([]cacheEntry, opts.glyphCacheEntries()),
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}
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a.subPixelX, a.subPixelBiasX, a.subPixelMaskX = opts.subPixelsX()
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a.subPixelY, a.subPixelBiasY, a.subPixelMaskY = opts.subPixelsY()
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// Fill the cache with invalid entries. Valid cache entries have fx and fy
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// in the range [0, 64).
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for i := range a.cache {
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a.cache[i].key.fy = 0xff
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}
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a.subPixelBiasX, a.subPixelMaskX = opts.subPixelsX()
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a.subPixelBiasY, a.subPixelMaskY = opts.subPixelsY()
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// Set the rasterizer's bounds to be big enough to handle the largest glyph.
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b := f.Bounds(a.scale)
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@ -148,9 +194,9 @@ func NewFace(f *Font, opts *Options) font.Face {
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ymax := -int(b.YMin-63) >> 6
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a.maxw = xmax - xmin
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a.maxh = ymax - ymin
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a.mask = image.NewAlpha(image.Rect(0, 0, a.maxw, a.maxh))
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a.masks = image.NewAlpha(image.Rect(0, 0, a.maxw, a.maxh*len(a.cache)))
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a.r.SetBounds(a.maxw, a.maxh)
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a.p = raster.NewAlphaSrcPainter(a.mask)
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a.p = facePainter{a}
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return a
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}
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@ -159,13 +205,17 @@ type face struct {
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f *Font
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hinting font.Hinting
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scale fixed.Int26_6
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subPixelX uint32
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subPixelBiasX fixed.Int26_6
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subPixelMaskX fixed.Int26_6
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subPixelY uint32
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subPixelBiasY fixed.Int26_6
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subPixelMaskY fixed.Int26_6
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mask *image.Alpha
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masks *image.Alpha
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cache []cacheEntry
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r raster.Rasterizer
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p raster.Painter
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paintOffset int
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maxw int
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maxh int
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glyphBuf GlyphBuf
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@ -199,23 +249,42 @@ func (a *face) Glyph(dot fixed.Point26_6, r rune) (
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ix, fx := int(dotX>>6), dotX&0x3f
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iy, fy := int(dotY>>6), dotY&0x3f
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advanceWidth, offset, gw, gh, ok := a.rasterize(a.f.Index(r), fx, fy)
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if !ok {
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return fixed.Point26_6{}, image.Rectangle{}, nil, image.Point{}, false
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index := a.f.Index(r)
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cIndex := uint32(index)
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cIndex = cIndex*a.subPixelX - uint32(fx/a.subPixelMaskX)
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cIndex = cIndex*a.subPixelY - uint32(fy/a.subPixelMaskY)
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cIndex &= uint32(len(a.cache) - 1)
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a.paintOffset = a.maxh * int(cIndex)
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k := cacheKey{
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index: index,
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fx: uint8(fx),
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fy: uint8(fy),
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}
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var v cacheVal
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if a.cache[cIndex].key != k {
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var ok bool
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v, ok = a.rasterize(index, fx, fy)
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if !ok {
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return fixed.Point26_6{}, image.Rectangle{}, nil, image.Point{}, false
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}
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a.cache[cIndex] = cacheEntry{k, v}
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} else {
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v = a.cache[cIndex].val
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}
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newDot = fixed.Point26_6{
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X: dot.X + advanceWidth,
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X: dot.X + v.advanceWidth,
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Y: dot.Y,
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}
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dr.Min = image.Point{
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X: ix + offset.X,
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Y: iy + offset.Y,
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X: ix + v.offset.X,
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Y: iy + v.offset.Y,
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}
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dr.Max = image.Point{
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X: dr.Min.X + gw,
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Y: dr.Min.Y + gh,
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X: dr.Min.X + v.gw,
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Y: dr.Min.Y + v.gh,
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}
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return newDot, dr, a.mask, image.Point{}, true
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return newDot, dr, a.masks, image.Point{Y: a.paintOffset}, true
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}
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func (a *face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
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@ -252,11 +321,9 @@ func (a *face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
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// the width and height of the given glyph at the given sub-pixel offsets.
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//
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// The 26.6 fixed point arguments fx and fy must be in the range [0, 1).
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func (a *face) rasterize(index Index, fx, fy fixed.Int26_6) (
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advanceWidth fixed.Int26_6, offset image.Point, gw int, gh int, ok bool) {
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func (a *face) rasterize(index Index, fx, fy fixed.Int26_6) (v cacheVal, ok bool) {
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if err := a.glyphBuf.Load(a.f, a.scale, index, a.hinting); err != nil {
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return 0, image.Point{}, 0, 0, false
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return cacheVal{}, false
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}
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// Calculate the integer-pixel bounds for the glyph.
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xmin := int(fx+a.glyphBuf.B.XMin) >> 6
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@ -264,7 +331,7 @@ func (a *face) rasterize(index Index, fx, fy fixed.Int26_6) (
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xmax := int(fx+a.glyphBuf.B.XMax+0x3f) >> 6
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ymax := int(fy-a.glyphBuf.B.YMin+0x3f) >> 6
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if xmin > xmax || ymin > ymax {
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return 0, image.Point{}, 0, 0, false
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return cacheVal{}, false
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}
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// A TrueType's glyph's nodes can have negative co-ordinates, but the
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// rasterizer clips anything left of x=0 or above y=0. xmin and ymin are
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@ -275,14 +342,20 @@ func (a *face) rasterize(index Index, fx, fy fixed.Int26_6) (
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fy -= fixed.Int26_6(ymin << 6)
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// Rasterize the glyph's vectors.
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a.r.Clear()
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clear(a.mask.Pix)
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pixOffset := a.paintOffset * a.maxw
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clear(a.masks.Pix[pixOffset : pixOffset+a.maxw*a.maxh])
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e0 := 0
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for _, e1 := range a.glyphBuf.End {
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a.drawContour(a.glyphBuf.Point[e0:e1], fx, fy)
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e0 = e1
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}
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a.r.Rasterize(a.p)
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return a.glyphBuf.AdvanceWidth, image.Point{xmin, ymin}, xmax - xmin, ymax - ymin, true
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return cacheVal{
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a.glyphBuf.AdvanceWidth,
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image.Point{xmin, ymin},
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xmax - xmin,
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ymax - ymin,
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}, true
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}
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func clear(pix []byte) {
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@ -364,3 +437,40 @@ func (a *face) drawContour(ps []Point, dx, dy fixed.Int26_6) {
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a.r.Add2(q0, start)
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}
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}
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// facePainter is like a raster.AlphaSrcPainter, with an additional Y offset
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// (face.paintOffset) to the painted spans.
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type facePainter struct {
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a *face
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}
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func (p facePainter) Paint(ss []raster.Span, done bool) {
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m := p.a.masks
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b := m.Bounds()
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b.Min.Y = p.a.paintOffset
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b.Max.Y = p.a.paintOffset + p.a.maxh
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for _, s := range ss {
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s.Y += p.a.paintOffset
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if s.Y < b.Min.Y {
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continue
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}
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if s.Y >= b.Max.Y {
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return
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}
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if s.X0 < b.Min.X {
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s.X0 = b.Min.X
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}
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if s.X1 > b.Max.X {
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s.X1 = b.Max.X
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}
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if s.X0 >= s.X1 {
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continue
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}
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base := (s.Y-m.Rect.Min.Y)*m.Stride - m.Rect.Min.X
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p := m.Pix[base+s.X0 : base+s.X1]
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color := uint8(s.A >> 24)
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for i := range p {
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p[i] = color
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}
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}
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}
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