Hi,
A lot of image operations like gamma adjustment, color inversion or
contrast enhancement can be expressed as a simple function applied
to each pixel. I have written a YUV(A) only filter to apply these
functions.
For example: color inversion becomes applyfn=255-Y:255-U:255-V.
If the pow function would be available a gamma correction would
look like this: applyfn=255*pow(Y/255\,0.25):U:V
Zeger Knops
Index: Makefile
===================================================================
--- Makefile (revision 4305)
+++ Makefile (working copy)
@@ -14,6 +14,7 @@
parseutils.o \
+OBJS-$(CONFIG_APPLYFN_FILTER) += vf_applyfn.o
OBJS-$(CONFIG_CROP_FILTER) += vf_crop.o
OBJS-$(CONFIG_DRAWBOX_FILTER) += vf_drawbox.o
OBJS-$(CONFIG_FPS_FILTER) += vf_fps.o
Index: allfilters.c
===================================================================
--- allfilters.c (revision 4305)
+++ allfilters.c (working copy)
@@ -34,6 +34,7 @@
return;
initialized = 1;
+ REGISTER_FILTER(APPLYFN,applyfn,vf);
REGISTER_FILTER(CROP,crop,vf);
REGISTER_FILTER(DRAWBOX,drawbox,vf);
REGISTER_FILTER(FIFO,fifo,vf);
Index: vf_applyfn.c
===================================================================
--- vf_applyfn.c (revision 0)
+++ vf_applyfn.c (revision 0)
@@ -0,0 +1,227 @@
+/*
+ * applyfn filter
+ * copyright (c) 2009 Zeger Knops
+ *
+ * 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
+ */
+
+/**
+ * Assume pow is available
+ * Gamma(g): applyfn=255*pow(Y/255\,g):U:V
+ *
+ * Assume the floor fn is available we can draw cartoons:
+ * applyfn=floor(Y/64)*64:floor(U/64)*64:floor(V/64)*64
+ *
+ * Assume the modulo fn is availabvle we can draw checkerboars
+ * applyfn=(modulo(floor(x/64)\,2)+modulo(floor(y/64)\,2))*Y
+ *
+ * B&W
+ * applyfn=Y:128:128
+ */
+
+#include "libavcodec/eval.h"
+#include "avfilter.h"
+#include "libavutil/avstring.h"
+
+enum PosOfValue {
+ POV_PI,
+ POV_E,
+ POV_N,
+ POV_W,
+ POV_H,
+ POV_x,
+ POV_y,
+ POV_Y,
+ POV_U,
+ POV_V,
+ POV_A,
+ POV_NULL
+};
+
+static const char *applyfn_symbols[POV_NULL+1]={
+ "PI",
+ "E",
+ "N", ///< frame number (starting at zero)
+ "W", ///< frame width
+ "H", ///< frame height
+ "x", ///< x position of current pixel
+ "y", ///< y position of current pixel
+ "Y", ///< Y value of current pixel
+ "U", ///< U value of current pixel
+ "V", ///< V value of current pixel
+ "A", ///< A value of current pixel
+ NULL
+};
+
+typedef struct
+{
+ AVEvalExpr *value_Y, *value_U, *value_V, *value_A;
+ int hsub, vsub;
+ double values[POV_NULL+1];
+} ApplyfnContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+ ApplyfnContext *applyfn = ctx->priv;
+ char Y_expr[256], U_expr[256], V_expr[256], A_expr[256];
+ const char *error;
+
+ applyfn->values[POV_PI ] = M_PI;
+ applyfn->values[POV_E ] = M_E;
+ applyfn->values[POV_N ] = 0.0;
+ applyfn->values[POV_NULL ] = 0.0;
+
+ av_strlcpy(Y_expr, "Y", sizeof(Y_expr));
+ av_strlcpy(U_expr, "U", sizeof(U_expr));
+ av_strlcpy(V_expr, "V", sizeof(V_expr));
+ av_strlcpy(A_expr, "A", sizeof(V_expr));
+
+ if (args)
+ sscanf(args, "%255[^:]:%255[^:]:%255[^:]:%255[^:]", Y_expr, U_expr, V_expr, A_expr)
+
+ applyfn->value_Y = ff_parse(Y_expr, applyfn_symbols,
+ NULL, NULL, NULL, NULL, &error);
+ if (!applyfn->value_Y )
+ av_log(ctx, AV_LOG_ERROR,
+ "init() cannot parse Y expression due to %s\n", error);
+
+ applyfn->value_U = ff_parse(U_expr, applyfn_symbols,
+ NULL, NULL, NULL, NULL, &error);
+ if (!applyfn->value_U )
+ av_log(ctx, AV_LOG_ERROR,
+ "init() cannot parse U expression due to %s\n", error);
+
+ applyfn->value_V = ff_parse(V_expr, applyfn_symbols,
+ NULL, NULL, NULL, NULL, &error);
+ if (!applyfn->value_V )
+ av_log(ctx, AV_LOG_ERROR,
+ "init() cannot parse V expression due to %s\n", error);
+
+ applyfn->value_A = ff_parse(A_expr, applyfn_symbols,
+ NULL, NULL, NULL, NULL, &error);
+ if (!applyfn->value_A )
+ av_log(ctx, AV_LOG_ERROR,
+ "init() cannot parse A expression due to %s\n", error);
+
+ return !applyfn->value_Y || !applyfn->value_U || !applyfn->value_V || !applyfn->value_A;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+ avfilter_set_common_formats(ctx,
+ avfilter_make_format_list(10,
+ PIX_FMT_YUV444P, PIX_FMT_YUV422P, PIX_FMT_YUV420P,
+ PIX_FMT_YUV411P, PIX_FMT_YUV410P,
+ PIX_FMT_YUVJ444P, PIX_FMT_YUVJ422P, PIX_FMT_YUVJ420P,
+ PIX_FMT_YUV440P, PIX_FMT_YUVJ440P,
+ PIX_FMT_YUVA420P));
+ return 0;
+}
+
+static int config_props(AVFilterLink *link)
+{
+ ApplyfnContext *applyfn = link->dst->priv;
+
+ avcodec_get_chroma_sub_sample(link->format, &applyfn->hsub, &applyfn->vsub);
+
+ return 0;
+}
+
+static void draw_slice(AVFilterLink *link, int y, int h)
+{
+ ApplyfnContext *applyfn = link->dst->priv;
+ AVFilterPicRef *in = link->cur_pic;
+ AVFilterPicRef *out = link->dst->outputs[0]->outpic;
+ uint8_t *inrow_0, *outrow_0, *alpharow, *outrow_1, *outrow_2, *inrow_1, *inrow_2;
+ int i, j, i_sub, j_sub, outrow_1_off, outrow_2_off, inrow_1_off, inrow_2_off;
+
+ applyfn->values[POV_N] += 1.0;
+ applyfn->values[POV_W] = link->w;
+ applyfn->values[POV_H] = h;
+
+ inrow_0 = in-> data[0] + y * in-> linesize[0];
+ outrow_0 = out->data[0] + y * out->linesize[0];
+
+ outrow_1_off = (y >> applyfn->vsub) * out->linesize[1];
+ outrow_2_off = (h >> applyfn->vsub ) * out->linesize[2] * ( link->w >> applyfn->hsub ) * (y >> applyfn->vsub);
+ inrow_1_off = (y >> applyfn->vsub) * in-> linesize[1];
+ inrow_2_off = (h >> applyfn->vsub ) * in-> linesize[2] * ( link->w >> applyfn->hsub ) * (y >> applyfn->vsub);
+
+ outrow_1 = outrow_1_off + out->data[1];
+ outrow_2 = outrow_2_off + out->data[2];
+ inrow_1 = outrow_1_off + in-> data[1];
+ inrow_2 = outrow_2_off + in-> data[2];
+
+ for(i = 0; i < h; i ++) {
+ applyfn->values[POV_y] = i;
+ i_sub = i >> applyfn->hsub;
+ for(j = 0; j < link->w; j ++)
+ {
+ j_sub = j >> applyfn->hsub;
+
+ applyfn->values[POV_x] = j;
+
+ applyfn->values[POV_Y] = inrow_0[j];
+ applyfn->values[POV_U] = inrow_1[j_sub];
+ applyfn->values[POV_V] = inrow_2[j_sub];
+
+ applyfn->values[POV_A] = out->data[3] ? alpharow[j] : 0;
+
+ outrow_0[j] = ff_parse_eval(applyfn->value_Y, applyfn->values, applyfn);
+ outrow_1[j_sub] = ff_parse_eval(applyfn->value_U, applyfn->values, applyfn);
+ outrow_2[j_sub] = ff_parse_eval(applyfn->value_V, applyfn->values, applyfn);
+
+ if ( out->data[3] )
+ alpharow[j] = ff_parse_eval(applyfn->value_A, applyfn->values, applyfn);
+
+ }
+ inrow_0 += in-> linesize[0];
+ outrow_0 += out->linesize[0];
+
+ if ( out->data[3] )
+ alpharow += out->linesize[3];
+
+ inrow_1 = inrow_1_off + in-> data[1] + i_sub * in-> linesize[1];
+ inrow_2 = inrow_2_off + in-> data[2] + i_sub * in-> linesize[2];
+ outrow_1 = outrow_1_off + out->data[1] + i_sub * out->linesize[1];
+ outrow_2 = outrow_2_off + out->data[2] + i_sub * out->linesize[2];
+ }
+
+ avfilter_draw_slice(link->dst->outputs[0], y, h);
+}
+
+AVFilter avfilter_vf_applyfn =
+{
+ .name = "applyfn",
+
+ .init = init,
+
+ .priv_size = sizeof(ApplyfnContext),
+
+ .query_formats = query_formats,
+
+ .inputs = (AVFilterPad[]) {{ .name = "default",
+ .type = CODEC_TYPE_VIDEO,
+ .draw_slice = draw_slice,
+ .config_props = config_props,
+ .min_perms = AV_PERM_READ, },
+ { .name = NULL}},
+ .outputs = (AVFilterPad[]) {{ .name = "default",
+ .type = CODEC_TYPE_VIDEO, },
+ { .name = NULL}},
+};
+
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