[FFmpeg-devel] [PATCH] Implement histogram equalization filter.
Stefano Sabatini
stefano.sabatini-lala
Sat Nov 20 16:44:01 CET 2010
---
configure | 1 +
libavfilter/Makefile | 1 +
libavfilter/allfilters.c | 1 +
libavfilter/vf_histeq.c | 217 ++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 220 insertions(+), 0 deletions(-)
create mode 100644 libavfilter/vf_histeq.c
diff --git a/configure b/configure
index 7dcb50f..4cca86c 100755
--- a/configure
+++ b/configure
@@ -1406,6 +1406,7 @@ udp_protocol_deps="network"
blackframe_filter_deps="gpl"
cropdetect_filter_deps="gpl"
frei0r_filter_deps="frei0r dlopen strtok_r"
+histeq_filter_deps="gpl"
ocv_smooth_filter_deps="libopencv"
yadif_filter_deps="gpl"
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 71dcf2a..3499b0f 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -28,6 +28,7 @@ OBJS-$(CONFIG_FIFO_FILTER) += vf_fifo.o
OBJS-$(CONFIG_FORMAT_FILTER) += vf_format.o
OBJS-$(CONFIG_FREI0R_FILTER) += vf_frei0r.o
OBJS-$(CONFIG_HFLIP_FILTER) += vf_hflip.o
+OBJS-$(CONFIG_HISTEQ_FILTER) += vf_histeq.o
OBJS-$(CONFIG_NOFORMAT_FILTER) += vf_format.o
OBJS-$(CONFIG_NULL_FILTER) += vf_null.o
OBJS-$(CONFIG_OCV_SMOOTH_FILTER) += vf_libopencv.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index d30e95a..c56319b 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -49,6 +49,7 @@ void avfilter_register_all(void)
REGISTER_FILTER (FORMAT, format, vf);
REGISTER_FILTER (FREI0R, frei0r, vf);
REGISTER_FILTER (HFLIP, hflip, vf);
+ REGISTER_FILTER (HISTEQ, histeq, vf);
REGISTER_FILTER (NOFORMAT, noformat, vf);
REGISTER_FILTER (NULL, null, vf);
REGISTER_FILTER (OCV_SMOOTH, ocv_smooth, vf);
diff --git a/libavfilter/vf_histeq.c b/libavfilter/vf_histeq.c
new file mode 100644
index 0000000..8578262
--- /dev/null
+++ b/libavfilter/vf_histeq.c
@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2010 Stefano Sabatini
+ * Copyright (c) 2001 Donald A. Graft
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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
+ * Histogram equalization filter, based on the VirtualDub filter by
+ * Donald A. Graft <neuron2 AT home DOT com>.
+ * Implements global automatic contrast adjustment by means of
+ * histogram equalization.
+ */
+
+/* #define DEBUG */
+
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+
+#define NONE 0
+#define WEAK 1
+#define STRONG 2
+
+typedef struct {
+ int strength;
+ int intensity;
+ int antibanding;
+ int in_histogram [256]; ///< input histogram
+ int out_histogram[256]; ///< output histogram
+ int LUT[256]; ///< lookup table derived from histogram[]
+ unsigned int jran, ia, ic, im;
+ int vsub, hsub;
+} HisteqContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+ HisteqContext *histeq = ctx->priv;
+ char antibanding_str[128] = "none";
+
+ histeq->strength = 200;
+ histeq->intensity = 210;
+ histeq->ia = 4096;
+ histeq->ic = 150889;
+ histeq->im = 714025;
+
+ if (args)
+ sscanf(args, "%d:%d:%s", &histeq->strength, &histeq->intensity, antibanding_str);
+
+ if (!strcmp(antibanding_str, "none" )) histeq->antibanding = NONE;
+ else if (!strcmp(antibanding_str, "weak" )) histeq->antibanding = WEAK;
+ else if (!strcmp(antibanding_str, "strong")) histeq->antibanding = STRONG;
+ else {
+ av_log(ctx, AV_LOG_ERROR, "Unknown value for antibanding '%s'.\n", antibanding_str);
+ return AVERROR(EINVAL);
+ }
+
+ av_log(ctx, AV_LOG_INFO, "strength:%d intensity:%d antibanding:%s\n",
+ histeq->strength, histeq->intensity, antibanding_str);
+
+ return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+ static const enum PixelFormat pix_fmts[] = {
+ PIX_FMT_YUV444P, PIX_FMT_YUV422P,
+ PIX_FMT_YUV420P, PIX_FMT_YUV411P,
+ PIX_FMT_YUV410P, PIX_FMT_YUV440P,
+ PIX_FMT_YUVA420P,
+ PIX_FMT_NONE
+ };
+
+ avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
+ return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ HisteqContext *histeq = ctx->priv;
+ const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
+
+ histeq->hsub = pix_desc->log2_chroma_w;
+ histeq->vsub = pix_desc->log2_chroma_h;
+
+ return 0;
+}
+
+static void null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir) { }
+
+static void end_frame(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ HisteqContext *histeq = ctx->priv;
+ AVFilterBufferRef *picref = inlink->cur_buf;
+ AVFilterLink *outlink = ctx->outputs[0];
+ int x, y, luthi, lutlo, lut, luma;
+ uint8_t *src;
+
+ /* Seed random generator for antibanding. */
+ histeq->jran = 739187UL;
+
+ /* Calculate and store the luminance and calculate the global histogram
+ based on the luminance. */
+ memset(histeq->in_histogram, 0, sizeof(histeq->in_histogram));
+ src = picref->data[0];
+ for (y = 0; y < inlink->h; y++) {
+ for (x = 0; x < inlink->w; x++)
+ histeq->in_histogram[src[x]]++;
+ src += picref->linesize[0];
+ }
+#ifdef DEBUG
+ for (x = 0; x < 256; x++)
+ av_log(ctx, AV_LOG_DEBUG, "in[%d]: %u\n", x, histeq->in_histogram[x]);
+#endif
+
+ /* Calculate the lookup table. */
+ histeq->LUT[0] = histeq->in_histogram[0];
+ /* Accumulate */
+ for (x = 1; x < 256; x++)
+ histeq->LUT[x] = histeq->LUT[x-1] + histeq->in_histogram[x];
+
+ /* Normalize. */
+ for (x = 0; x < 256; x++)
+ histeq->LUT[x] = (histeq->LUT[x] * histeq->intensity) / (inlink->h * inlink->w);
+
+ /* Adjust the LUT based on the selected strength. This is an alpha
+ mix of the calculated LUT and a linear LUT with gain 1. */
+ for (x = 0; x < 256; x++)
+ histeq->LUT[x] = (histeq->strength * histeq->LUT[x]) / 255 +
+ ((255 - histeq->strength) * x) / 255;
+
+ /* Output the equalized frame. */
+ memset(histeq->out_histogram, 0, sizeof(histeq->out_histogram));
+
+ src = picref->data[0];
+ for (y = 0; y < inlink->h; y++) {
+ for (x = 0; x < inlink->w; x++) {
+ luma = src[x];
+ if (luma == 0) {
+ src[x] = 0;
+ histeq->out_histogram[0]++;
+ } else {
+ lut = histeq->LUT[luma];
+ if (histeq->antibanding != NONE) {
+ if (luma > 0) {
+ lutlo = histeq->antibanding == WEAK ?
+ (histeq->LUT[luma] + histeq->LUT[luma-1]) / 2 :
+ histeq->LUT[luma-1];
+ } else
+ lutlo = lut;
+
+ if (luma < 255) {
+ luthi = (histeq->antibanding == WEAK) ?
+ (histeq->LUT[luma] + histeq->LUT[luma+1]) / 2 :
+ histeq->LUT[luma+1];
+ } else
+ luthi = lut;
+
+ if (lutlo != luthi) {
+ histeq->jran = (histeq->jran * histeq->ia + histeq->ic) % histeq->im;
+ lut = lutlo + ((luthi - lutlo + 1) * histeq->jran) / histeq->im;
+ }
+ }
+ src[x] = src[x] * lut / luma;
+ histeq->out_histogram[src[x]]++;
+ }
+ }
+ src += picref->linesize[0];
+ }
+#ifdef DEBUG
+ for (x = 0; x < 256; x++)
+ av_log(ctx, AV_LOG_DEBUG, "out[%d]: %u\n", x, histeq->out_histogram[x]);
+#endif
+
+ avfilter_draw_slice(outlink, 0, picref->video->h, 1);
+ avfilter_end_frame(outlink);
+}
+
+AVFilter avfilter_vf_histeq = {
+ .name = "histeq",
+ .description = NULL_IF_CONFIG_SMALL("Perform global color histogram equalization."),
+
+ .priv_size = sizeof(HisteqContext),
+ .init = init,
+ .query_formats = query_formats,
+
+ .inputs = (AVFilterPad[]) {{ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .config_props = config_input,
+ .get_video_buffer = avfilter_null_get_video_buffer,
+ .start_frame = avfilter_null_start_frame,
+ .draw_slice = null_draw_slice,
+ .end_frame = end_frame,
+ .min_perms = AV_PERM_WRITE | AV_PERM_READ,
+ .rej_perms = AV_PERM_PRESERVE },
+ { .name = NULL}},
+
+ .outputs = (AVFilterPad[]) {{ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO, },
+ { .name = NULL}},
+};
--
1.7.1
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