golang-image/font/basicfont/basicfont.go
Nigel Tao f1e9747265 font: add Metrics.Descent.
Change-Id: Id38e7e54264e0e77a28afd8e10cf574610b47336
Reviewed-on: https://go-review.googlesource.com/21019
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2016-03-23 23:23:04 +00:00

123 lines
3.2 KiB
Go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:generate go run gen.go
// Package basicfont provides fixed-size font faces.
package basicfont // import "golang.org/x/image/font/basicfont"
import (
"image"
"golang.org/x/image/font"
"golang.org/x/image/math/fixed"
)
// Range maps a contiguous range of runes to vertically adjacent sub-images of
// a Face's Mask image. The rune range is inclusive on the low end and
// exclusive on the high end.
//
// If Low <= r && r < High, then the rune r is mapped to the sub-image of
// Face.Mask whose bounds are image.Rect(0, y, Face.Width, y+Face.Height),
// where y equals (int(r-Low) + Offset) * Face.Height.
type Range struct {
Low, High rune
Offset int
}
// Face7x13 is a Face derived from the public domain X11 misc-fixed font files.
//
// At the moment, it holds the printable characters in ASCII starting with
// space, and the Unicode replacement character U+FFFD.
//
// Its data is entirely self-contained and does not require loading from
// separate files.
var Face7x13 = &Face{
Advance: 7,
Width: 6,
Height: 13,
Ascent: 11,
Mask: mask7x13,
Ranges: []Range{
{'\u0020', '\u007f', 0},
{'\ufffd', '\ufffe', 95},
},
}
// Face is a basic font face whose glyphs all have the same metrics.
//
// It is safe to use concurrently.
type Face struct {
// Advance is the glyph advance, in pixels.
Advance int
// Width is the glyph width, in pixels.
Width int
// Height is the glyph height, in pixels.
Height int
// Ascent is the glyph ascent, in pixels.
Ascent int
// TODO: do we also need Top and Left fields?
// Mask contains all of the glyph masks. Its width is typically the Face's
// Width, and its height a multiple of the Face's Height.
Mask image.Image
// Ranges map runes to sub-images of Mask. The rune ranges must not
// overlap, and must be in increasing rune order.
Ranges []Range
}
func (f *Face) Close() error { return nil }
func (f *Face) Kern(r0, r1 rune) fixed.Int26_6 { return 0 }
func (f *Face) Metrics() font.Metrics {
return font.Metrics{
Height: fixed.I(f.Height),
Ascent: fixed.I(f.Ascent),
Descent: fixed.I(f.Height - f.Ascent),
}
}
func (f *Face) Glyph(dot fixed.Point26_6, r rune) (
dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
loop:
for _, rr := range [2]rune{r, '\ufffd'} {
for _, rng := range f.Ranges {
if rr < rng.Low || rng.High <= rr {
continue
}
maskp.Y = (int(rr-rng.Low) + rng.Offset) * f.Height
ok = true
break loop
}
}
if !ok {
return image.Rectangle{}, nil, image.Point{}, 0, false
}
minX := int(dot.X+32) >> 6
minY := int(dot.Y+32)>>6 - f.Ascent
dr = image.Rectangle{
Min: image.Point{
X: minX,
Y: minY,
},
Max: image.Point{
X: minX + f.Width,
Y: minY + f.Height,
},
}
return dr, f.Mask, maskp, fixed.I(f.Advance), true
}
func (f *Face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
return fixed.R(0, -f.Ascent, f.Width, -f.Ascent+f.Height), fixed.I(f.Advance), true
}
func (f *Face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
return fixed.I(f.Advance), true
}