lavfi: add ICC profile support via lcms2

This introduces an optional dependency on lcms2 into FFmpeg. lcms2 is a
widely used library for ICC profile handling, which apart from being
used in almost all major image processing programs and video players,
has also been deployed in browsers. As such, it's both widely available
and well-tested.

Add a few helpers to cover our major use cases. This commit merely
introduces the helpers (and configure check), even though nothing uses
them yet.

It's worth pointing out that the reason the cmsToneCurves for each
AVCOL_TRC are cached inside the context, is because constructing a
cmsToneCurve requires evaluating the curve at 4096 (by default) grid
points and constructing a LUT. So, we ideally only want to do this once
per curve. This matters for e.g. ff_icc_profile_detect_transfer, which
essentially compares a profile against all of these generated LUTs.
Re-generating the LUTs for every iteration would be unnecessarily
wasteful.

The same consideration does not apply to e.g. cmsCreate*Profile, which
is a very lightweight operation just involving struct allocation and
setting a few pointers.

The cutoff value of 0.01 was determined by experimentation. The lowest
"false positive" delta I saw in practice was 0.13, and the largest
"false negative" delta was 0.0008. So a value of 0.01 sits comfortaby
almost exactly in the middle.

Signed-off-by: Niklas Haas <git@haasn.dev>

1 files changed, 310 insertions, 0 deletions

diff --git a/libavfilter/fflcms2.c b/libavfilter/fflcms2.c
new file mode 100644
index 0000000000..efc7cb5189
--- /dev/null
+++ b/libavfilter/fflcms2.c
@@ -0,0 +1,310 @@
+/*
+ * Copyright (c) 2022 Niklas Haas
+ * 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
+ */
+
+#include "libavutil/color_utils.h"
+
+#include "fflcms2.h"
+
+static void log_cb(cmsContext ctx, cmsUInt32Number error, const char *str)
+{
+    FFIccContext *s = cmsGetContextUserData(ctx);
+    av_log(s->avctx, AV_LOG_ERROR, "lcms2: [%"PRIu32"] %s\n", error, str);
+}
+
+int ff_icc_context_init(FFIccContext *s, void *avctx)
+{
+    memset(s, 0, sizeof(*s));
+    s->avctx = avctx;
+    s->ctx = cmsCreateContext(NULL, s);
+    if (!s->ctx)
+        return AVERROR(ENOMEM);
+
+    cmsSetLogErrorHandlerTHR(s->ctx, log_cb);
+    return 0;
+}
+
+void ff_icc_context_uninit(FFIccContext *s)
+{
+    for (int i = 0; i < FF_ARRAY_ELEMS(s->curves); i++)
+        cmsFreeToneCurve(s->curves[i]);
+    cmsDeleteContext(s->ctx);
+    memset(s, 0, sizeof(*s));
+}
+
+static int get_curve(FFIccContext *s, enum AVColorTransferCharacteristic trc,
+                     cmsToneCurve **out_curve)
+{
+    if (trc >= AVCOL_TRC_NB)
+        return AVERROR_INVALIDDATA;
+
+    if (s->curves[trc])
+        goto done;
+
+    switch (trc) {
+    case AVCOL_TRC_LINEAR:
+        s->curves[trc] = cmsBuildGamma(s->ctx, 1.0);
+        break;
+    case AVCOL_TRC_GAMMA22:
+        s->curves[trc] = cmsBuildGamma(s->ctx, 2.2);
+        break;
+    case AVCOL_TRC_GAMMA28:
+        s->curves[trc] = cmsBuildGamma(s->ctx, 2.8);
+        break;
+    case AVCOL_TRC_BT709:
+    case AVCOL_TRC_SMPTE170M:
+    case AVCOL_TRC_BT2020_10:
+    case AVCOL_TRC_BT2020_12:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 4, (double[5]) {
+            /* γ = */ 1/0.45,
+            /* a = */ 1/1.099296826809442,
+            /* b = */ 1 - 1/1.099296826809442,
+            /* c = */ 1/4.5,
+            /* d = */ 4.5 * 0.018053968510807,
+        });
+        break;
+    case AVCOL_TRC_SMPTE240M:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 4, (double[5]) {
+            /* γ = */ 1/0.45,
+            /* a = */ 1/1.1115,
+            /* b = */ 1 - 1/1.1115,
+            /* c = */ 1/4.0,
+            /* d = */ 4.0 * 0.0228,
+        });
+        break;
+    case AVCOL_TRC_LOG:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 8, (double[5]) {
+            /* a = */ 1.0,
+            /* b = */ 10.0,
+            /* c = */ 2.0,
+            /* d = */ -1.0,
+            /* e = */ 0.0
+        });
+        break;
+    case AVCOL_TRC_LOG_SQRT:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 8, (double[5]) {
+            /* a = */ 1.0,
+            /* b = */ 10.0,
+            /* c = */ 2.5,
+            /* d = */ -1.0,
+            /* e = */ 0.0
+        });
+        break;
+    case AVCOL_TRC_IEC61966_2_1:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 4, (double[5]) {
+            /* γ = */ 2.4,
+            /* a = */ 1/1.055,
+            /* b = */ 1 - 1/1.055,
+            /* c = */ 1/12.92,
+            /* d = */ 12.92 * 0.0031308,
+        });
+        break;
+    case AVCOL_TRC_SMPTE428:
+        s->curves[trc] = cmsBuildParametricToneCurve(s->ctx, 2, (double[3]) {
+            /* γ = */ 2.6,
+            /* a = */ pow(52.37/48.0, 1/2.6),
+            /* b = */ 0.0
+        });
+        break;
+
+    /* Can't be represented using the existing parametric tone curves.
+     * FIXME: use cmsBuildTabulatedToneCurveFloat instead */
+    case AVCOL_TRC_IEC61966_2_4:
+    case AVCOL_TRC_BT1361_ECG:
+    case AVCOL_TRC_SMPTE2084:
+    case AVCOL_TRC_ARIB_STD_B67:
+        return AVERROR_PATCHWELCOME;
+
+    default:
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (!s->curves[trc])
+        return AVERROR(ENOMEM);
+
+done:
+    *out_curve = s->curves[trc];
+    return 0;
+}
+
+int ff_icc_profile_generate(FFIccContext *s,
+                            enum AVColorPrimaries color_prim,
+                            enum AVColorTransferCharacteristic color_trc,
+                            cmsHPROFILE *out_profile)
+{
+    cmsToneCurve *tonecurve;
+    const struct ColorPrimaries *prim;
+    int ret;
+
+    if (!(prim = ff_get_color_primaries(color_prim)))
+        return AVERROR_INVALIDDATA;
+    if ((ret = get_curve(s, color_trc, &tonecurve)) < 0)
+        return ret;
+
+    *out_profile = cmsCreateRGBProfileTHR(s->ctx,
+        &(cmsCIExyY) { prim->wp.xw, prim->wp.yw, 1.0 },
+        &(cmsCIExyYTRIPLE) {
+            .Red    = { prim->prim.xr, prim->prim.yr, 1.0 },
+            .Green  = { prim->prim.xg, prim->prim.yg, 1.0 },
+            .Blue   = { prim->prim.xb, prim->prim.yb, 1.0 },
+        },
+        (cmsToneCurve *[3]) { tonecurve, tonecurve, tonecurve }
+    );
+
+    return *out_profile == NULL ? AVERROR(ENOMEM) : 0;
+}
+
+int ff_icc_profile_attach(FFIccContext *s, cmsHPROFILE profile, AVFrame *frame)
+{
+    cmsUInt32Number size;
+    AVBufferRef *buf;
+
+    if (!cmsSaveProfileToMem(profile, NULL, &size))
+        return AVERROR_EXTERNAL;
+
+    buf = av_buffer_alloc(size);
+    if (!buf)
+        return AVERROR(ENOMEM);
+
+    if (!cmsSaveProfileToMem(profile, buf->data, &size) || size != buf->size) {
+        av_buffer_unref(&buf);
+        return AVERROR_EXTERNAL;
+    }
+
+    if (!av_frame_new_side_data_from_buf(frame, AV_FRAME_DATA_ICC_PROFILE, buf)) {
+        av_buffer_unref(&buf);
+        return AVERROR(ENOMEM);
+    }
+
+    return 0;
+}
+
+static av_always_inline void XYZ_xy(cmsCIEXYZ XYZ, double *x, double *y)
+{
+    double k = 1.0 / (XYZ.X + XYZ.Y + XYZ.Z);
+    *x = k * XYZ.X;
+    *y = k * XYZ.Y;
+}
+
+int ff_icc_profile_read_primaries(FFIccContext *s, cmsHPROFILE profile,
+                                  struct ColorPrimaries *out_primaries)
+{
+    static const uint8_t testprimaries[4][3] = {
+        { 0xFF,    0,    0 }, /* red */
+        {    0, 0xFF,    0 }, /* green */
+        {    0,    0, 0xFF }, /* blue */
+        { 0xFF, 0xFF, 0xFF }, /* white */
+    };
+
+    struct WhitepointCoefficients *wp = &out_primaries->wp;
+    struct PrimaryCoefficients *prim = &out_primaries->prim;
+    cmsFloat64Number prev_adapt;
+    cmsHPROFILE xyz;
+    cmsHTRANSFORM tf;
+    cmsCIEXYZ dst[4];
+
+    xyz = cmsCreateXYZProfileTHR(s->ctx);
+    if (!xyz)
+        return AVERROR(ENOMEM);
+
+    /* We need to use an unadapted observer to get the raw values */
+    prev_adapt = cmsSetAdaptationStateTHR(s->ctx, 0.0);
+    tf = cmsCreateTransformTHR(s->ctx, profile, TYPE_RGB_8, xyz, TYPE_XYZ_DBL,
+                               INTENT_ABSOLUTE_COLORIMETRIC,
+                               /* Note: These flags mostly don't do anything
+                                * anyway, but specify them regardless */
+                               cmsFLAGS_NOCACHE |
+                               cmsFLAGS_NOOPTIMIZE |
+                               cmsFLAGS_LOWRESPRECALC |
+                               cmsFLAGS_GRIDPOINTS(2));
+    cmsSetAdaptationStateTHR(s->ctx, prev_adapt);
+    cmsCloseProfile(xyz);
+    if (!tf) {
+        av_log(s->avctx, AV_LOG_ERROR, "Invalid ICC profile (e.g. CMYK)\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    cmsDoTransform(tf, testprimaries, dst, 4);
+    cmsDeleteTransform(tf);
+    XYZ_xy(dst[0], &prim->xr, &prim->yr);
+    XYZ_xy(dst[1], &prim->xg, &prim->yg);
+    XYZ_xy(dst[2], &prim->xb, &prim->yb);
+    XYZ_xy(dst[3], &wp->xw, &wp->yw);
+    return 0;
+}
+
+int ff_icc_profile_detect_transfer(FFIccContext *s, cmsHPROFILE profile,
+                                   enum AVColorTransferCharacteristic *out_trc)
+{
+    /* 8-bit linear grayscale ramp */
+    static const uint8_t testramp[16][3] = {
+        {  1,   1,   1}, /* avoid exact zero due to log100 etc. */
+        { 17,  17,  17},
+        { 34,  34,  34},
+        { 51,  51,  51},
+        { 68,  68,  68},
+        { 85,  85,  85},
+        { 02,  02,  02},
+        {119, 119, 119},
+        {136, 136, 136},
+        {153, 153, 153},
+        {170, 170, 170},
+        {187, 187, 187},
+        {204, 204, 204},
+        {221, 221, 221},
+        {238, 238, 238},
+        {255, 255, 255},
+    };
+
+    double dst[FF_ARRAY_ELEMS(testramp)];
+
+    for (enum AVColorTransferCharacteristic trc = 0; trc < AVCOL_TRC_NB; trc++) {
+        cmsToneCurve *tonecurve;
+        cmsHPROFILE ref;
+        cmsHTRANSFORM tf;
+        double delta = 0.0;
+        if (get_curve(s, trc, &tonecurve) < 0)
+            continue;
+
+        ref = cmsCreateGrayProfileTHR(s->ctx, cmsD50_xyY(), tonecurve);
+        if (!ref)
+            return AVERROR(ENOMEM);
+
+        tf = cmsCreateTransformTHR(s->ctx, profile, TYPE_RGB_8, ref, TYPE_GRAY_DBL,
+                                   INTENT_RELATIVE_COLORIMETRIC,
+                                   cmsFLAGS_NOCACHE | cmsFLAGS_NOOPTIMIZE);
+        cmsCloseProfile(ref);
+        if (!tf) {
+            av_log(s->avctx, AV_LOG_ERROR, "Invalid ICC profile (e.g. CMYK)\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        cmsDoTransform(tf, testramp, dst, FF_ARRAY_ELEMS(dst));
+        cmsDeleteTransform(tf);
+
+        for (int i = 0; i < FF_ARRAY_ELEMS(dst); i++)
+            delta += fabs(testramp[i][0] / 255.0 - dst[i]);
+        if (delta < 0.01) {
+            *out_trc = trc;
+            return 0;
+        }
+    }
+
+    *out_trc = AVCOL_TRC_UNSPECIFIED;
+    return 0;
+}