-
Notifications
You must be signed in to change notification settings - Fork 7
/
SceneEncoder.go
182 lines (163 loc) · 4.94 KB
/
SceneEncoder.go
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
package compression
import (
"context"
"errors"
"fmt"
)
// EncodedFrame contains the streams of one compressed frame.
type EncodedFrame struct {
Bitstream []byte
Maskstream []byte
}
type tileDelta [PixelPerTile]byte
type frameDelta struct {
tiles []tileDelta
}
// SceneEncoder encodes an entire scene of bitmaps sharing the same palette.
type SceneEncoder struct {
hTiles int
vTiles int
lineStride int
tileStride int
lastFrame []byte
deltas []frameDelta
}
// NewSceneEncoder returns a new instance.
func NewSceneEncoder(width, height int) *SceneEncoder {
e := &SceneEncoder{
hTiles: width / TileSideLength,
vTiles: height / TileSideLength,
lineStride: width,
}
e.tileStride = e.lineStride * TileSideLength
e.lastFrame = make([]byte, e.vTiles*TileSideLength*e.lineStride)
return e
}
// AddFrame registers a further frame to the scene.
func (e *SceneEncoder) AddFrame(frame []byte) error {
if len(frame) != len(e.lastFrame) {
return errors.New("invalid frame size")
}
var delta frameDelta
isFirstFrame := len(e.deltas) == 0
vStart := 0
for vTile := 0; vTile < e.vTiles; vTile++ {
tileStart := vStart
for hTile := 0; hTile < e.hTiles; hTile++ {
delta.tiles = append(delta.tiles, e.deltaTile(isFirstFrame, tileStart, frame))
tileStart += TileSideLength
}
vStart += e.tileStride
}
e.deltas = append(e.deltas, delta)
copy(e.lastFrame, frame)
return nil
}
func (e *SceneEncoder) deltaTile(isFirstFrame bool, offset int, frame []byte) tileDelta {
var delta tileDelta
for y := 0; y < TileSideLength; y++ {
start := offset + (y * e.lineStride)
for x := 0; x < TileSideLength; x++ {
pixel := frame[start+x]
if isFirstFrame || (pixel != e.lastFrame[start+x]) {
delta[y*TileSideLength+x] = pixel
}
}
}
return delta
}
// Encode processes all the previously registered frames and creates the necessary components for decoding.
func (e *SceneEncoder) Encode(ctx context.Context) (
words []ControlWord, paletteLookupBuffer []byte, frames []EncodedFrame, err error) {
var wordSequencer ControlWordSequencer
tileColorOpsPerFrame := make([][]TileColorOp, len(e.deltas))
paletteLookup, err := e.createPaletteLookup(ctx)
if err != nil {
return
}
paletteLookupBuffer = paletteLookup.Buffer()
if len(paletteLookupBuffer) > 0x1FFFF {
err = fmt.Errorf("palette lookup is too big: %vB", len(paletteLookupBuffer))
return
}
frames = make([]EncodedFrame, len(e.deltas))
for frameIndex := 0; frameIndex < len(e.deltas); frameIndex++ {
var maskstreamWriter MaskstreamWriter
outFrame := &frames[frameIndex]
delta := e.deltas[frameIndex]
lastOp := TileColorOp{Type: CtrlUnknown}
for tileIndex, tile := range delta.tiles {
var op TileColorOp
paletteIndex, pal, mask := paletteLookup.Lookup(tile)
palSize := len(pal)
switch {
case palSize == 1 && (pal[0] == 0x00):
op.Type = CtrlSkip
case palSize == 1:
op.Type = CtrlColorTile2ColorsStatic
op.Offset = uint32(pal[0])<<8 | uint32(pal[0])
case palSize == 2 && mask == 0xAAAA && (pal[0] != 0x00) && (pal[1] != 0x00):
op.Type = CtrlColorTile2ColorsStatic
op.Offset = uint32(pal[1])<<8 | uint32(pal[0])
case palSize == 2 && mask == 0x5555 && (pal[0] != 0x00) && (pal[1] != 0x00):
op.Type = CtrlColorTile2ColorsStatic
op.Offset = uint32(pal[0])<<8 | uint32(pal[1])
case palSize <= 2:
op.Type = CtrlColorTile2ColorsMasked
if palSize == 2 {
op.Offset = uint32(pal[1])
op.Offset <<= 8
}
if palSize > 0 {
op.Offset |= uint32(pal[0])
}
_ = maskstreamWriter.Write(2, mask)
case palSize <= 4:
op.Type = CtrlColorTile4ColorsMasked
op.Offset = uint32(paletteIndex)
_ = maskstreamWriter.Write(4, mask)
case palSize <= 8:
op.Type = CtrlColorTile8ColorsMasked
op.Offset = uint32(paletteIndex)
_ = maskstreamWriter.Write(6, mask)
default:
op.Type = CtrlColorTile16ColorsMasked
op.Offset = uint32(paletteIndex)
_ = maskstreamWriter.Write(8, mask)
}
if op.Type != CtrlSkip && (tileIndex%e.hTiles) != 0 && lastOp == op {
op = TileColorOp{Type: CtrlRepeatPrevious}
} else {
lastOp = op
}
err = wordSequencer.Add(op)
if err != nil {
return nil, nil, nil, err
}
tileColorOpsPerFrame[frameIndex] = append(tileColorOpsPerFrame[frameIndex], op)
}
outFrame.Maskstream = maskstreamWriter.Buffer
}
wordSequence, err := wordSequencer.Sequence()
if err != nil {
return nil, nil, nil, err
}
wordSequence.HTiles = uint32(e.hTiles)
words = wordSequence.ControlWords()
for frameIndex, ops := range tileColorOpsPerFrame {
frames[frameIndex].Bitstream, err = wordSequence.BitstreamFor(ops)
if err != nil {
return nil, nil, nil, err
}
}
return
}
func (e *SceneEncoder) createPaletteLookup(ctx context.Context) (PaletteLookup, error) {
var paletteLookupGenerator PaletteLookupGenerator
for _, delta := range e.deltas {
for _, tile := range delta.tiles {
paletteLookupGenerator.Add(tile)
}
}
return paletteLookupGenerator.Generate(ctx)
}