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>

1 files changed, 106 insertions, 0 deletions

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 */