summaryrefslogtreecommitdiffstats
path: root/vendor/golang.org/x/image/bmp/writer.go
blob: f07b39dba19ab90df1ebd1ef9b7f9d8a1e1fea59 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
// Copyright 2013 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.

package bmp

import (
	"encoding/binary"
	"errors"
	"image"
	"io"
)

type header struct {
	sigBM           [2]byte
	fileSize        uint32
	resverved       [2]uint16
	pixOffset       uint32
	dibHeaderSize   uint32
	width           uint32
	height          uint32
	colorPlane      uint16
	bpp             uint16
	compression     uint32
	imageSize       uint32
	xPixelsPerMeter uint32
	yPixelsPerMeter uint32
	colorUse        uint32
	colorImportant  uint32
}

func encodePaletted(w io.Writer, pix []uint8, dx, dy, stride, step int) error {
	var padding []byte
	if dx < step {
		padding = make([]byte, step-dx)
	}
	for y := dy - 1; y >= 0; y-- {
		min := y*stride + 0
		max := y*stride + dx
		if _, err := w.Write(pix[min:max]); err != nil {
			return err
		}
		if padding != nil {
			if _, err := w.Write(padding); err != nil {
				return err
			}
		}
	}
	return nil
}

func encodeRGBA(w io.Writer, pix []uint8, dx, dy, stride, step int, opaque bool) error {
	buf := make([]byte, step)
	if opaque {
		for y := dy - 1; y >= 0; y-- {
			min := y*stride + 0
			max := y*stride + dx*4
			off := 0
			for i := min; i < max; i += 4 {
				buf[off+2] = pix[i+0]
				buf[off+1] = pix[i+1]
				buf[off+0] = pix[i+2]
				off += 3
			}
			if _, err := w.Write(buf); err != nil {
				return err
			}
		}
	} else {
		for y := dy - 1; y >= 0; y-- {
			min := y*stride + 0
			max := y*stride + dx*4
			off := 0
			for i := min; i < max; i += 4 {
				a := uint32(pix[i+3])
				if a == 0 {
					buf[off+2] = 0
					buf[off+1] = 0
					buf[off+0] = 0
					buf[off+3] = 0
					off += 4
					continue
				} else if a == 0xff {
					buf[off+2] = pix[i+0]
					buf[off+1] = pix[i+1]
					buf[off+0] = pix[i+2]
					buf[off+3] = 0xff
					off += 4
					continue
				}
				buf[off+2] = uint8(((uint32(pix[i+0]) * 0xffff) / a) >> 8)
				buf[off+1] = uint8(((uint32(pix[i+1]) * 0xffff) / a) >> 8)
				buf[off+0] = uint8(((uint32(pix[i+2]) * 0xffff) / a) >> 8)
				buf[off+3] = uint8(a)
				off += 4
			}
			if _, err := w.Write(buf); err != nil {
				return err
			}
		}
	}
	return nil
}

func encodeNRGBA(w io.Writer, pix []uint8, dx, dy, stride, step int, opaque bool) error {
	buf := make([]byte, step)
	if opaque {
		for y := dy - 1; y >= 0; y-- {
			min := y*stride + 0
			max := y*stride + dx*4
			off := 0
			for i := min; i < max; i += 4 {
				buf[off+2] = pix[i+0]
				buf[off+1] = pix[i+1]
				buf[off+0] = pix[i+2]
				off += 3
			}
			if _, err := w.Write(buf); err != nil {
				return err
			}
		}
	} else {
		for y := dy - 1; y >= 0; y-- {
			min := y*stride + 0
			max := y*stride + dx*4
			off := 0
			for i := min; i < max; i += 4 {
				buf[off+2] = pix[i+0]
				buf[off+1] = pix[i+1]
				buf[off+0] = pix[i+2]
				buf[off+3] = pix[i+3]
				off += 4
			}
			if _, err := w.Write(buf); err != nil {
				return err
			}
		}
	}
	return nil
}

func encode(w io.Writer, m image.Image, step int) error {
	b := m.Bounds()
	buf := make([]byte, step)
	for y := b.Max.Y - 1; y >= b.Min.Y; y-- {
		off := 0
		for x := b.Min.X; x < b.Max.X; x++ {
			r, g, b, _ := m.At(x, y).RGBA()
			buf[off+2] = byte(r >> 8)
			buf[off+1] = byte(g >> 8)
			buf[off+0] = byte(b >> 8)
			off += 3
		}
		if _, err := w.Write(buf); err != nil {
			return err
		}
	}
	return nil
}

// Encode writes the image m to w in BMP format.
func Encode(w io.Writer, m image.Image) error {
	d := m.Bounds().Size()
	if d.X < 0 || d.Y < 0 {
		return errors.New("bmp: negative bounds")
	}
	h := &header{
		sigBM:         [2]byte{'B', 'M'},
		fileSize:      14 + 40,
		pixOffset:     14 + 40,
		dibHeaderSize: 40,
		width:         uint32(d.X),
		height:        uint32(d.Y),
		colorPlane:    1,
	}

	var step int
	var palette []byte
	var opaque bool
	switch m := m.(type) {
	case *image.Gray:
		step = (d.X + 3) &^ 3
		palette = make([]byte, 1024)
		for i := 0; i < 256; i++ {
			palette[i*4+0] = uint8(i)
			palette[i*4+1] = uint8(i)
			palette[i*4+2] = uint8(i)
			palette[i*4+3] = 0xFF
		}
		h.imageSize = uint32(d.Y * step)
		h.fileSize += uint32(len(palette)) + h.imageSize
		h.pixOffset += uint32(len(palette))
		h.bpp = 8

	case *image.Paletted:
		step = (d.X + 3) &^ 3
		palette = make([]byte, 1024)
		for i := 0; i < len(m.Palette) && i < 256; i++ {
			r, g, b, _ := m.Palette[i].RGBA()
			palette[i*4+0] = uint8(b >> 8)
			palette[i*4+1] = uint8(g >> 8)
			palette[i*4+2] = uint8(r >> 8)
			palette[i*4+3] = 0xFF
		}
		h.imageSize = uint32(d.Y * step)
		h.fileSize += uint32(len(palette)) + h.imageSize
		h.pixOffset += uint32(len(palette))
		h.bpp = 8
	case *image.RGBA:
		opaque = m.Opaque()
		if opaque {
			step = (3*d.X + 3) &^ 3
			h.bpp = 24
		} else {
			step = 4 * d.X
			h.bpp = 32
		}
		h.imageSize = uint32(d.Y * step)
		h.fileSize += h.imageSize
	case *image.NRGBA:
		opaque = m.Opaque()
		if opaque {
			step = (3*d.X + 3) &^ 3
			h.bpp = 24
		} else {
			step = 4 * d.X
			h.bpp = 32
		}
		h.imageSize = uint32(d.Y * step)
		h.fileSize += h.imageSize
	default:
		step = (3*d.X + 3) &^ 3
		h.imageSize = uint32(d.Y * step)
		h.fileSize += h.imageSize
		h.bpp = 24
	}

	if err := binary.Write(w, binary.LittleEndian, h); err != nil {
		return err
	}
	if palette != nil {
		if err := binary.Write(w, binary.LittleEndian, palette); err != nil {
			return err
		}
	}

	if d.X == 0 || d.Y == 0 {
		return nil
	}

	switch m := m.(type) {
	case *image.Gray:
		return encodePaletted(w, m.Pix, d.X, d.Y, m.Stride, step)
	case *image.Paletted:
		return encodePaletted(w, m.Pix, d.X, d.Y, m.Stride, step)
	case *image.RGBA:
		return encodeRGBA(w, m.Pix, d.X, d.Y, m.Stride, step, opaque)
	case *image.NRGBA:
		return encodeNRGBA(w, m.Pix, d.X, d.Y, m.Stride, step, opaque)
	}
	return encode(w, m, step)
}