0
# Scaling and Format Conversion
1

2
Video scaling, pixel format conversion, and color space transformations using FFmpeg's libswscale with optimized implementations for performance.
3

4
## Capabilities
5

6
### Scaling Context Management
7

8
#### Context Operations
9

10
```java { .api }
11
/**
12
 * Allocate and initialize scaling context
13
 * @param srcW Source width
14
 * @param srcH Source height  
15
 * @param srcFormat Source pixel format
16
 * @param dstW Destination width
17
 * @param dstH Destination height
18
 * @param dstFormat Destination pixel format
19
 * @param flags Scaling algorithm flags
20
 * @param srcFilter Source filter (optional)
21
 * @param dstFilter Destination filter (optional)
22
 * @param param Additional parameters (optional)
23
 * @return Scaling context or null on failure
24
 */
25
SwsContext sws_getContext(int srcW, int srcH, int srcFormat,
26
    int dstW, int dstH, int dstFormat, int flags,
27
    SwsFilter srcFilter, SwsFilter dstFilter, DoublePointer param);
28

29
/**
30
 * Free scaling context
31
 * @param swsContext Context to free
32
 */
33
void sws_freeContext(SwsContext swsContext);
34

35
/**
36
 * Scale image data
37
 * @param c Scaling context
38
 * @param srcSlice Source image planes
39
 * @param srcStride Source line strides
40
 * @param srcSliceY Starting Y position
41
 * @param srcSliceH Height to process
42
 * @param dst Destination image planes
43
 * @param dstStride Destination line strides
44
 * @return Height of output slice
45
 */
46
int sws_scale(SwsContext c, PointerPointer srcSlice, IntPointer srcStride,
47
    int srcSliceY, int srcSliceH, PointerPointer dst, IntPointer dstStride);
48
```
49

50
**Usage Example:**
51

52
```java
53
import org.bytedeco.ffmpeg.swscale.*;
54
import static org.bytedeco.ffmpeg.global.swscale.*;
55
import static org.bytedeco.ffmpeg.global.avutil.*;
56

57
// Create scaling context: 1920x1080 -> 640x480, YUV420P -> RGB24
58
SwsContext swsContext = sws_getContext(
59
    1920, 1080, AV_PIX_FMT_YUV420P,    // Source
60
    640, 480, AV_PIX_FMT_RGB24,        // Destination  
61
    SWS_BILINEAR,                       // Scaling algorithm
62
    null, null, (DoublePointer)null     // Optional filters/params
63
);
64

65
if (swsContext == null) {
66
    throw new RuntimeException("Cannot create scaling context");
67
}
68

69
// Allocate destination frame
70
AVFrame dstFrame = av_frame_alloc();
71
dstFrame.width(640);
72
dstFrame.height(480);
73
dstFrame.format(AV_PIX_FMT_RGB24);
74
av_frame_get_buffer(dstFrame, 32);
75

76
// Scale source frame to destination
77
AVFrame srcFrame = /* ... source frame ... */;
78
int result = sws_scale(
79
    swsContext,
80
    srcFrame.data(), srcFrame.linesize(),
81
    0, srcFrame.height(),
82
    dstFrame.data(), dstFrame.linesize()
83
);
84

85
System.out.println("Scaled " + result + " lines");
86

87
// Cleanup
88
av_frame_free(dstFrame);
89
sws_freeContext(swsContext);
90
```
91

92
### Advanced Scaling
93

94
#### Cached Context Operations
95

96
```java { .api }
97
/**
98
 * Scale with cached context (allocates if needed)
99
 * @param context Pointer to context (null initially)
100
 * @param srcW Source width
101
 * @param srcH Source height
102
 * @param srcFormat Source format
103
 * @param dstW Destination width
104
 * @param dstH Destination height
105
 * @param dstFormat Destination format
106
 * @param flags Scaling flags
107
 * @param srcFilter Source filter
108
 * @param dstFilter Destination filter
109
 * @param param Parameters
110
 * @return Scaling context
111
 */
112
SwsContext sws_getCachedContext(SwsContext context,
113
    int srcW, int srcH, int srcFormat,
114
    int dstW, int dstH, int dstFormat, int flags,
115
    SwsFilter srcFilter, SwsFilter dstFilter, DoublePointer param);
116

117
/**
118
 * Check if scaling is supported
119
 * @param pix_fmt Pixel format
120
 * @return 1 if supported for input, 2 if supported for output
121
 */
122
int sws_isSupportedInput(int pix_fmt);
123
int sws_isSupportedOutput(int pix_fmt);
124
```
125

126
### Vector Operations
127

128
#### SIMD Optimizations
129

130
```java { .api }
131
/**
132
 * Get CPU flags for optimization
133
 * @return CPU capability flags
134
 */
135
int av_get_cpu_flags();
136

137
/**
138
 * Initialize scaling context with CPU optimizations
139
 * @param c Scaling context
140
 * @param srcFilter Source filter
141
 * @param dstFilter Destination filter
142
 * @return 0 on success
143
 */
144
int sws_init_context(SwsContext c, SwsFilter srcFilter, SwsFilter dstFilter);
145
```
146

147
### Color Space Operations
148

149
#### Color Space Information
150

151
```java { .api }
152
/**
153
 * Get coefficients for color space conversion
154
 * @param colorspace Color space (BT.709, BT.601, etc.)
155
 * @return Color space coefficients
156
 */
157
IntPointer sws_getCoefficients(int colorspace);
158

159
/**
160
 * Set color space conversion parameters
161
 * @param c Scaling context
162
 * @param inv_table Inverse color table
163
 * @param fullRange Full range flag
164
 * @param table Color conversion table
165
 * @param srcRange Source range
166
 * @param dstRange Destination range
167
 * @param brightness Brightness adjustment
168
 * @param contrast Contrast adjustment
169
 * @param saturation Saturation adjustment
170
 * @return 0 on success
171
 */
172
int sws_setColorspaceDetails(SwsContext c, IntPointer inv_table, int fullRange,
173
    IntPointer table, int srcRange, int dstRange, int brightness, int contrast, int saturation);
174
```
175

176
## Constants
177

178
### Scaling Algorithms
179

180
```java { .api }
181
// Scaling algorithm flags
182
int SWS_FAST_BILINEAR = 1;      // Fast bilinear
183
int SWS_BILINEAR = 2;           // Bilinear
184
int SWS_BICUBIC = 4;            // Bicubic  
185
int SWS_X = 8;                  // Experimental
186
int SWS_POINT = 0x10;           // Nearest neighbor
187
int SWS_AREA = 0x20;            // Area averaging
188
int SWS_BICUBLIN = 0x40;        // Bicubic for luma, bilinear for chroma
189
int SWS_GAUSS = 0x80;           // Gaussian
190
int SWS_SINC = 0x100;           // Sinc
191
int SWS_LANCZOS = 0x200;        // Lanczos
192
int SWS_SPLINE = 0x400;         // Spline
193
```
194

195
### Pixel Formats
196

197
```java { .api }
198
// Common pixel formats for scaling
199
int AV_PIX_FMT_YUV420P = 0;     // Planar YUV 4:2:0
200
int AV_PIX_FMT_RGB24 = 2;       // Packed RGB 8:8:8
201
int AV_PIX_FMT_BGR24 = 3;       // Packed BGR 8:8:8
202
int AV_PIX_FMT_YUV422P = 4;     // Planar YUV 4:2:2
203
int AV_PIX_FMT_YUV444P = 5;     // Planar YUV 4:4:4
204
int AV_PIX_FMT_RGBA = 26;       // Packed RGBA 8:8:8:8
205
int AV_PIX_FMT_BGRA = 27;       // Packed BGRA 8:8:8:8
206
int AV_PIX_FMT_NV12 = 23;       // Semi-planar YUV 4:2:0
207
int AV_PIX_FMT_NV21 = 24;       // Semi-planar YUV 4:2:0
208
```
209

210
### Color Space Constants
211

212
```java { .api }
213
// Color space standards
214
int SWS_CS_ITU709 = 1;          // ITU-R BT.709
215
int SWS_CS_FCC = 4;             // FCC
216
int SWS_CS_ITU601 = 5;          // ITU-R BT.601
217
int SWS_CS_SMPTE170M = 6;       // SMPTE-170M
218
int SWS_CS_SMPTE240M = 7;       // SMPTE-240M
219
int SWS_CS_DEFAULT = 5;         // Default (BT.601)
220
```