github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/image/font/basicfont/basicfont.go (about) 1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 //go:generate go run gen.go 6 7 // Package basicfont provides fixed-size font faces. 8 package basicfont // import "golang.org/x/image/font/basicfont" 9 10 import ( 11 "image" 12 13 "golang.org/x/image/math/fixed" 14 ) 15 16 // Range maps a contiguous range of runes to vertically adjacent sub-images of 17 // a Face's Mask image. The rune range is inclusive on the low end and 18 // exclusive on the high end. 19 // 20 // If Low <= r && r < High, then the rune r is mapped to the sub-image of 21 // Face.Mask whose bounds are image.Rect(0, y, Face.Width, y+Face.Height), 22 // where y equals (int(r-Low) + Offset) * Face.Height. 23 type Range struct { 24 Low, High rune 25 Offset int 26 } 27 28 // Face7x13 is a Face derived from the public domain X11 misc-fixed font files. 29 // 30 // At the moment, it holds the printable characters in ASCII starting with 31 // space, and the Unicode replacement character U+FFFD. 32 // 33 // Its data is entirely self-contained and does not require loading from 34 // separate files. 35 var Face7x13 = &Face{ 36 Advance: 7, 37 Width: 6, 38 Height: 13, 39 Ascent: 11, 40 Mask: mask7x13, 41 Ranges: []Range{ 42 {'\u0020', '\u007f', 0}, 43 {'\ufffd', '\ufffe', 95}, 44 }, 45 } 46 47 // Face is a basic font face whose glyphs all have the same metrics. 48 // 49 // It is safe to use concurrently. 50 type Face struct { 51 // Advance is the glyph advance, in pixels. 52 Advance int 53 // Width is the glyph width, in pixels. 54 Width int 55 // Height is the glyph height, in pixels. 56 Height int 57 // Ascent is the glyph ascent, in pixels. 58 Ascent int 59 60 // TODO: do we also need Top and Left fields? 61 62 // Mask contains all of the glyph masks. Its width is typically the Face's 63 // Width, and its height a multiple of the Face's Height. 64 Mask image.Image 65 // Ranges map runes to sub-images of Mask. The rune ranges must not 66 // overlap, and must be in increasing rune order. 67 Ranges []Range 68 } 69 70 func (f *Face) Close() error { return nil } 71 func (f *Face) Kern(r0, r1 rune) fixed.Int26_6 { return 0 } 72 73 func (f *Face) Glyph(dot fixed.Point26_6, r rune) ( 74 dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) { 75 76 loop: 77 for _, rr := range [2]rune{r, '\ufffd'} { 78 for _, rng := range f.Ranges { 79 if rr < rng.Low || rng.High <= rr { 80 continue 81 } 82 maskp.Y = (int(rr-rng.Low) + rng.Offset) * f.Height 83 ok = true 84 break loop 85 } 86 } 87 if !ok { 88 return image.Rectangle{}, nil, image.Point{}, 0, false 89 } 90 91 minX := int(dot.X+32) >> 6 92 minY := int(dot.Y+32)>>6 - f.Ascent 93 dr = image.Rectangle{ 94 Min: image.Point{ 95 X: minX, 96 Y: minY, 97 }, 98 Max: image.Point{ 99 X: minX + f.Width, 100 Y: minY + f.Height, 101 }, 102 } 103 104 return dr, f.Mask, maskp, fixed.I(f.Advance), true 105 } 106 107 func (f *Face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) { 108 return fixed.R(0, -f.Ascent, f.Width, -f.Ascent+f.Height), fixed.I(f.Advance), true 109 } 110 111 func (f *Face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) { 112 return fixed.I(f.Advance), true 113 }