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swscale: organize and better document flags

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Group them into an enum rather than random #defines, and document their
behavior a bit more obviously.

Of particular note, I discovered that SWS_DIRECT_BGR is not referenced
anywhere else in the code base. As such, I have moved it to the deprecated
section, alongside SWS_ERROR_DIFFUSION.

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
pull/391/head
Niklas Haas 6 months ago
parent 6a91a165fd
commit fb16964009
3 changed files with 70 additions and 51 deletions
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  1. 3
      doc/APIchanges
  2. 116
      libswscale/swscale.h
  3. 2
      libswscale/version.h

3
doc/APIchanges
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@ -2,6 +2,9 @@ The last version increases of all libraries were on 2024-03-07
API changes, most recent first:
2024-11-25 - xxxxxxxxxx - lsws 8.11.100 - swscale.h
Replace #define-based SWS_* flags by enum SwsFlags.
2024-11-25 - xxxxxxxxxx - lsws 8.10.100 - swscale.h
Publicly expose struct SwsContext, enum SwsDither, and enum SwsAlphaBlend.

116
libswscale/swscale.h
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@ -91,6 +91,71 @@ typedef enum SwsAlphaBlend {
SWS_ALPHA_BLEND_NB, /* not part of the ABI */
} SwsAlphaBlend;
typedef enum SwsFlags {
/**
* Scaler selection options. Only one may be active at a time.
*/
SWS_FAST_BILINEAR = 1 << 0, ///< fast bilinear filtering
SWS_BILINEAR = 1 << 1, ///< bilinear filtering
SWS_BICUBIC = 1 << 2, ///< 2-tap cubic B-spline
SWS_X = 1 << 3, ///< experimental
SWS_POINT = 1 << 4, ///< nearest neighbor
SWS_AREA = 1 << 5, ///< area averaging
SWS_BICUBLIN = 1 << 6, ///< bicubic luma, bilinear chroma
SWS_GAUSS = 1 << 7, ///< gaussian approximation
SWS_SINC = 1 << 8, ///< unwindowed sinc
SWS_LANCZOS = 1 << 9, ///< 3-tap sinc/sinc
SWS_SPLINE = 1 << 10, ///< cubic Keys spline
/**
* Emit verbose log of scaling parameters.
*/
SWS_PRINT_INFO = 1 << 12,
/**
* Perform full chroma upsampling when upscaling to RGB.
*
* For example, when converting 50x50 yuv420p to 100x100 rgba, setting this flag
* will scale the chroma plane from 25x25 to 100x100 (4:4:4), and then convert
* the 100x100 yuv444p image to rgba in the final output step.
*
* Without this flag, the chroma plane is instead scaled to 50x100 (4:2:2),
* with a single chroma sample being re-used for both of the horizontally
* adjacent RGBA output pixels.
*/
SWS_FULL_CHR_H_INT = 1 << 13,
/**
* Perform full chroma interpolation when downscaling RGB sources.
*
* For example, when converting a 100x100 rgba source to 50x50 yuv444p, setting
* this flag will generate a 100x100 (4:4:4) chroma plane, which is then
* downscaled to the required 50x50.
*
* Without this flag, the chroma plane is instead generated at 50x100 (dropping
* every other pixel), before then being downscaled to the required 50x50
* resolution.
*/
SWS_FULL_CHR_H_INP = 1 << 14,
/**
* Force bit-exact output. This will prevent the use of platform-specific
* optimizations that may lead to slight difference in rounding, in favor
* of always maintaining exact bit output compatibility with the reference
* C code.
*
* Note: It is recommended to set both of these flags simultaneously.
*/
SWS_ACCURATE_RND = 1 << 18,
SWS_BITEXACT = 1 << 19,
/**
* Deprecated flags.
*/
SWS_DIRECT_BGR = 1 << 15, ///< This flag has no effect
SWS_ERROR_DIFFUSION = 1 << 23, ///< Set `SwsContext.dither` instead
} SwsFlags;
/***********************************
* Context creation and management *
***********************************/
@ -109,7 +174,7 @@ typedef struct SwsContext {
void *opaque;
/**
* Bitmask of SWS_*.
* Bitmask of SWS_*. See `SwsFlags` for details.
*/
unsigned flags;
@ -225,60 +290,11 @@ int sws_test_frame(const AVFrame *frame, int output);
*/
int sws_is_noop(const AVFrame *dst, const AVFrame *src);
/* values for the flags, the stuff on the command line is different */
#define SWS_FAST_BILINEAR 1
#define SWS_BILINEAR 2
#define SWS_BICUBIC 4
#define SWS_X 8
#define SWS_POINT 0x10
#define SWS_AREA 0x20
#define SWS_BICUBLIN 0x40
#define SWS_GAUSS 0x80
#define SWS_SINC 0x100
#define SWS_LANCZOS 0x200
#define SWS_SPLINE 0x400
#define SWS_SRC_V_CHR_DROP_MASK 0x30000
#define SWS_SRC_V_CHR_DROP_SHIFT 16
#define SWS_PARAM_DEFAULT 123456
#define SWS_PRINT_INFO 0x1000
//the following 3 flags are not completely implemented
/**
* Perform full chroma upsampling when upscaling to RGB.
*
* For example, when converting 50x50 yuv420p to 100x100 rgba, setting this flag
* will scale the chroma plane from 25x25 to 100x100 (4:4:4), and then convert
* the 100x100 yuv444p image to rgba in the final output step.
*
* Without this flag, the chroma plane is instead scaled to 50x100 (4:2:2),
* with a single chroma sample being re-used for both of the horizontally
* adjacent RGBA output pixels.
*/
#define SWS_FULL_CHR_H_INT 0x2000
/**
* Perform full chroma interpolation when downscaling RGB sources.
*
* For example, when converting a 100x100 rgba source to 50x50 yuv444p, setting
* this flag will generate a 100x100 (4:4:4) chroma plane, which is then
* downscaled to the required 50x50.
*
* Without this flag, the chroma plane is instead generated at 50x100 (dropping
* every other pixel), before then being downscaled to the required 50x50
* resolution.
*/
#define SWS_FULL_CHR_H_INP 0x4000
#define SWS_DIRECT_BGR 0x8000
#define SWS_ACCURATE_RND 0x40000
#define SWS_BITEXACT 0x80000
#define SWS_ERROR_DIFFUSION 0x800000
#define SWS_MAX_REDUCE_CUTOFF 0.002
#define SWS_CS_ITU709 1

2
libswscale/version.h
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@ -28,7 +28,7 @@
#include "version_major.h"
#define LIBSWSCALE_VERSION_MINOR 10
#define LIBSWSCALE_VERSION_MINOR 11
#define LIBSWSCALE_VERSION_MICRO 100
#define LIBSWSCALE_VERSION_INT AV_VERSION_INT(LIBSWSCALE_VERSION_MAJOR, \

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