avutil/csp: create public API for colorspace structs

This commit moves some of the functionality from avfilter/colorspace
into avutil/csp and exposes it as a public API so it can be used by
libavcodec and/or libavformat. It also converts those structs from
double values to AVRational to make regression testing easier and
more consistent.

Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

4 files changed, 237 insertions, 1 deletions

diff --git a/libavutil/Makefile b/libavutil/Makefile
index 234de62a4b..74d21a8103 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -20,6 +20,7 @@ HEADERS = adler32.h                                                     \
           common.h                                                      \
           cpu.h                                                         \
           crc.h                                                         \
+          csp.h                                                         \
           des.h                                                         \
           detection_bbox.h                                              \
           dict.h                                                        \
@@ -113,6 +114,7 @@ OBJS = adler32.o                                                        \
        color_utils.o                                                    \
        cpu.o                                                            \
        crc.o                                                            \
+       csp.o                                                            \
        des.o                                                            \
        detection_bbox.o                                                 \
        dict.o                                                           \
diff --git a/libavutil/csp.c b/libavutil/csp.c
new file mode 100644
index 0000000000..98fc83c1da
--- /dev/null
+++ b/libavutil/csp.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file Colorspace functions for libavutil
+ * @author Ronald S. Bultje <rsbultje@gmail.com>
+ * @author Leo Izen <leo.izen@gmail.com>
+ */
+
+#include <stdlib.h>
+
+#include "attributes.h"
+#include "csp.h"
+#include "pixfmt.h"
+#include "rational.h"
+
+#define AVR(d) { (int)(d * 100000 + 0.5), 100000 }
+
+/*
+ * All constants explained in e.g. https://linuxtv.org/downloads/v4l-dvb-apis/ch02s06.html
+ * The older ones (bt470bg/m) are also explained in their respective ITU docs
+ * (e.g. https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.470-5-199802-S!!PDF-E.pdf)
+ * whereas the newer ones can typically be copied directly from wikipedia :)
+ */
+static const struct AVLumaCoefficients luma_coefficients[AVCOL_SPC_NB] = {
+    [AVCOL_SPC_FCC]        = { AVR(0.30),   AVR(0.59),   AVR(0.11)   },
+    [AVCOL_SPC_BT470BG]    = { AVR(0.299),  AVR(0.587),  AVR(0.114)  },
+    [AVCOL_SPC_SMPTE170M]  = { AVR(0.299),  AVR(0.587),  AVR(0.114)  },
+    [AVCOL_SPC_BT709]      = { AVR(0.2126), AVR(0.7152), AVR(0.0722) },
+    [AVCOL_SPC_SMPTE240M]  = { AVR(0.212),  AVR(0.701),  AVR(0.087)  },
+    [AVCOL_SPC_YCOCG]      = { AVR(0.25),   AVR(0.5),    AVR(0.25)   },
+    [AVCOL_SPC_RGB]        = { AVR(1),      AVR(1),      AVR(1)      },
+    [AVCOL_SPC_BT2020_NCL] = { AVR(0.2627), AVR(0.6780), AVR(0.0593) },
+    [AVCOL_SPC_BT2020_CL]  = { AVR(0.2627), AVR(0.6780), AVR(0.0593) },
+};
+
+const struct AVLumaCoefficients *av_csp_luma_coeffs_from_avcsp(enum AVColorSpace csp)
+{
+    const AVLumaCoefficients *coeffs;
+
+    if (csp >= AVCOL_SPC_NB)
+        return NULL;
+    coeffs = &luma_coefficients[csp];
+    if (!coeffs->cr.num)
+        return NULL;
+
+    return coeffs;
+}
+
+#define WP_D65 { AVR(0.3127), AVR(0.3290) }
+#define WP_C   { AVR(0.3100), AVR(0.3160) }
+#define WP_DCI { AVR(0.3140), AVR(0.3510) }
+#define WP_E   { {1, 3}, {1, 3} }
+
+static const AVColorPrimariesDesc color_primaries[AVCOL_PRI_NB] = {
+    [AVCOL_PRI_BT709]     = { WP_D65, { { AVR(0.640), AVR(0.330) }, { AVR(0.300), AVR(0.600) }, { AVR(0.150), AVR(0.060) } } },
+    [AVCOL_PRI_BT470M]    = { WP_C,   { { AVR(0.670), AVR(0.330) }, { AVR(0.210), AVR(0.710) }, { AVR(0.140), AVR(0.080) } } },
+    [AVCOL_PRI_BT470BG]   = { WP_D65, { { AVR(0.640), AVR(0.330) }, { AVR(0.290), AVR(0.600) }, { AVR(0.150), AVR(0.060) } } },
+    [AVCOL_PRI_SMPTE170M] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.310), AVR(0.595) }, { AVR(0.155), AVR(0.070) } } },
+    [AVCOL_PRI_SMPTE240M] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.310), AVR(0.595) }, { AVR(0.155), AVR(0.070) } } },
+    [AVCOL_PRI_SMPTE428]  = { WP_E,   { { AVR(0.735), AVR(0.265) }, { AVR(0.274), AVR(0.718) }, { AVR(0.167), AVR(0.009) } } },
+    [AVCOL_PRI_SMPTE431]  = { WP_DCI, { { AVR(0.680), AVR(0.320) }, { AVR(0.265), AVR(0.690) }, { AVR(0.150), AVR(0.060) } } },
+    [AVCOL_PRI_SMPTE432]  = { WP_D65, { { AVR(0.680), AVR(0.320) }, { AVR(0.265), AVR(0.690) }, { AVR(0.150), AVR(0.060) } } },
+    [AVCOL_PRI_FILM]      = { WP_C,   { { AVR(0.681), AVR(0.319) }, { AVR(0.243), AVR(0.692) }, { AVR(0.145), AVR(0.049) } } },
+    [AVCOL_PRI_BT2020]    = { WP_D65, { { AVR(0.708), AVR(0.292) }, { AVR(0.170), AVR(0.797) }, { AVR(0.131), AVR(0.046) } } },
+    [AVCOL_PRI_JEDEC_P22] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.295), AVR(0.605) }, { AVR(0.155), AVR(0.077) } } },
+};
+
+const AVColorPrimariesDesc *av_csp_primaries_desc_from_id(enum AVColorPrimaries prm)
+{
+    const AVColorPrimariesDesc *p;
+
+    if (prm >= AVCOL_PRI_NB)
+        return NULL;
+    p = &color_primaries[prm];
+    if (!p->prim.r.x.num)
+        return NULL;
+
+    return p;
+}
+
+static av_always_inline AVRational abs_sub_q(AVRational r1, AVRational r2)
+{
+    AVRational diff = av_sub_q(r1, r2);
+    /* denominator assumed to be positive */
+    return av_make_q(abs(diff.num), diff.den);
+}
+
+enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm)
+{
+    AVRational delta;
+
+    for (enum AVColorPrimaries p = 0; p < AVCOL_PRI_NB; p++) {
+        const AVColorPrimariesDesc *ref = &color_primaries[p];
+        if (!ref->prim.r.x.num)
+            continue;
+
+        delta = abs_sub_q(prm->prim.r.x, ref->prim.r.x);
+        delta = av_add_q(delta, abs_sub_q(prm->prim.r.y, ref->prim.r.y));
+        delta = av_add_q(delta, abs_sub_q(prm->prim.g.x, ref->prim.g.x));
+        delta = av_add_q(delta, abs_sub_q(prm->prim.g.y, ref->prim.g.y));
+        delta = av_add_q(delta, abs_sub_q(prm->prim.b.x, ref->prim.b.x));
+        delta = av_add_q(delta, abs_sub_q(prm->prim.b.y, ref->prim.b.y));
+        delta = av_add_q(delta, abs_sub_q(prm->wp.x, ref->wp.x));
+        delta = av_add_q(delta, abs_sub_q(prm->wp.y, ref->wp.y));
+
+        if (av_cmp_q(delta, av_make_q(1, 1000)) < 0)
+            return p;
+    }
+
+    return AVCOL_PRI_UNSPECIFIED;
+}
diff --git a/libavutil/csp.h b/libavutil/csp.h
new file mode 100644
index 0000000000..37544449c6
--- /dev/null
+++ b/libavutil/csp.h
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_CSP_H
+#define AVUTIL_CSP_H
+
+#include "pixfmt.h"
+#include "rational.h"
+
+/**
+ * @file Colorspace value utility functions for libavutil.
+ * @author Ronald S. Bultje <rsbultje@gmail.com>
+ * @author Leo Izen <leo.izen@gmail.com>
+ * @defgroup lavu_math_csp Colorspace Utility
+ * @ingroup lavu_math
+ * @{
+ */
+
+/**
+ * Struct containing luma coefficients to be used for RGB to YUV/YCoCg, or similar
+ * calculations.
+ */
+typedef struct AVLumaCoefficients {
+    AVRational cr, cg, cb;
+} AVLumaCoefficients;
+
+/**
+ * Struct containing chromaticity x and y values for the standard CIE 1931
+ * chromaticity definition.
+ */
+typedef struct AVCIExy {
+    AVRational x, y;
+} AVCIExy;
+
+/**
+ * Struct defining the red, green, and blue primary locations in terms of CIE
+ * 1931 chromaticity x and y.
+ */
+typedef struct AVPrimaryCoefficients {
+    AVCIExy r, g, b;
+} AVPrimaryCoefficients;
+
+/**
+ * Struct defining white point location in terms of CIE 1931 chromaticity x
+ * and y.
+ */
+typedef AVCIExy AVWhitepointCoefficients;
+
+/**
+ * Struct that contains both white point location and primaries location, providing
+ * the complete description of a color gamut.
+ */
+typedef struct AVColorPrimariesDesc {
+    AVWhitepointCoefficients wp;
+    AVPrimaryCoefficients prim;
+} AVColorPrimariesDesc;
+
+/**
+ * Retrieves the Luma coefficients necessary to construct a conversion matrix
+ * from an enum constant describing the colorspace.
+ * @param csp An enum constant indicating YUV or similar colorspace.
+ * @return The Luma coefficients associated with that colorspace, or NULL
+ *     if the constant is unknown to libavutil.
+ */
+const AVLumaCoefficients *av_csp_luma_coeffs_from_avcsp(enum AVColorSpace csp);
+
+/**
+ * Retrieves a complete gamut description from an enum constant describing the
+ * color primaries.
+ * @param prm An enum constant indicating primaries
+ * @return A description of the colorspace gamut associated with that enum
+ *     constant, or NULL if the constant is unknown to libavutil.
+ */
+const AVColorPrimariesDesc *av_csp_primaries_desc_from_id(enum AVColorPrimaries prm);
+
+/**
+ * Detects which enum AVColorPrimaries constant corresponds to the given complete
+ * gamut description.
+ * @see enum AVColorPrimaries
+ * @param prm A description of the colorspace gamut
+ * @return The enum constant associated with this gamut, or
+ *     AVCOL_PRI_UNSPECIFIED if no clear match can be idenitified.
+ */
+enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm);
+
+/**
+ * @}
+ */
+
+#endif /* AVUTIL_CSP_H */
diff --git a/libavutil/version.h b/libavutil/version.h
index 1b4b41d81f..2c7f4f6b37 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  57
-#define LIBAVUTIL_VERSION_MINOR  25
+#define LIBAVUTIL_VERSION_MINOR  26
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \