avfilter: add epx pixel art scaler

Changelog

@@ -56,6 +56,7 @@ version <next>:
 - shufflepixels filter
 - tmidequalizer filter
 - estdif filter
+- epx filter
 
 
 version 4.3:

doc/filters.texi

@@ -10943,6 +10943,18 @@ Can be either @var{normal} or @var{diff}. Default is @var{normal}.
 between neighbour histogram values.
 @end table
 
+@section epx
+Apply the EPX magnification filter which is designed for pixel art.
+
+It accepts the following option:
+
+@table @option
+@item n
+Set the scaling dimension: @code{2} for @code{2xEPX}, @code{3} for
+@code{3xEPX}.
+Default is @code{3}.
+@end table
+
 @section eq
 Set brightness, contrast, saturation and approximate gamma adjustment.
 

libavfilter/Makefile

@@ -248,6 +248,7 @@ OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
 OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o
 OBJS-$(CONFIG_ELBG_FILTER)                   += vf_elbg.o
 OBJS-$(CONFIG_ENTROPY_FILTER)                += vf_entropy.o
+OBJS-$(CONFIG_EPX_FILTER)                    += vf_epx.o
 OBJS-$(CONFIG_EQ_FILTER)                     += vf_eq.o
 OBJS-$(CONFIG_EROSION_FILTER)                += vf_neighbor.o
 OBJS-$(CONFIG_EROSION_OPENCL_FILTER)         += vf_neighbor_opencl.o opencl.o \

libavfilter/allfilters.c

@@ -234,6 +234,7 @@ extern AVFilter ff_vf_drawtext;
 extern AVFilter ff_vf_edgedetect;
 extern AVFilter ff_vf_elbg;
 extern AVFilter ff_vf_entropy;
+extern AVFilter ff_vf_epx;
 extern AVFilter ff_vf_eq;
 extern AVFilter ff_vf_erosion;
 extern AVFilter ff_vf_erosion_opencl;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  96
+#define LIBAVFILTER_VERSION_MINOR  97
 #define LIBAVFILTER_VERSION_MICRO 100
 
 

libavfilter/vf_epx.c

@@ -0,0 +1,287 @@
+/*
+ * 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/opt.h"
+#include "libavutil/avassert.h"
+#include "libavutil/pixdesc.h"
+#include "internal.h"
+
+typedef struct EPXContext {
+    const AVClass *class;
+
+    int n;
+
+    int (*epx_slice)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
+} EPXContext;
+
+typedef struct ThreadData {
+    AVFrame *in, *out;
+} ThreadData;
+
+#define OFFSET(x) offsetof(EPXContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption epx_options[] = {
+    { "n", "set scale factor", OFFSET(n), AV_OPT_TYPE_INT, {.i64 = 3}, 2, 3, .flags = FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(epx);
+
+static int epx2_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    ThreadData *td = arg;
+    const AVFrame *in = td->in;
+    AVFrame *out = td->out;
+    const int slice_start = (in->height *  jobnr   ) / nb_jobs;
+    const int slice_end   = (in->height * (jobnr+1)) / nb_jobs;
+
+    for (int p = 0; p < 1; p++) {
+        const int width = in->width;
+        const int height = in->height;
+        const int src_linesize = in->linesize[p] / 4;
+        const int dst_linesize = out->linesize[p] / 4;
+        const uint32_t *src = (const uint32_t *)in->data[p];
+        uint32_t *dst = (uint32_t *)out->data[p];
+        const uint32_t *src_line[3];
+
+        src_line[0] = src + src_linesize * FFMAX(slice_start - 1, 0);
+        src_line[1] = src + src_linesize * slice_start;
+        src_line[2] = src + src_linesize * FFMIN(slice_start + 1, height-1);
+
+        for (int y = slice_start; y < slice_end; y++) {
+            uint32_t *dst_line[2];
+
+            dst_line[0] = dst + dst_linesize*2*y;
+            dst_line[1] = dst + dst_linesize*(2*y+1);
+
+            for (int x = 0; x < width; x++) {
+                uint32_t E0, E1, E2, E3;
+                uint32_t B, D, E, F, H;
+
+                B = src_line[0][x];
+                D = src_line[1][FFMAX(x-1, 0)];
+                E = src_line[1][x];
+                F = src_line[1][FFMIN(x+1, width - 1)];
+                H = src_line[2][x];
+
+                if (B != H && D != F) {
+                    E0 = D == B ? D : E;
+                    E1 = B == F ? F : E;
+                    E2 = D == H ? D : E;
+                    E3 = H == F ? F : E;
+                } else {
+                    E0 = E;
+                    E1 = E;
+                    E2 = E;
+                    E3 = E;
+                }
+
+                dst_line[0][x*2]   = E0;
+                dst_line[0][x*2+1] = E1;
+                dst_line[1][x*2]   = E2;
+                dst_line[1][x*2+1] = E3;
+            }
+
+            src_line[0] = src_line[1];
+            src_line[1] = src_line[2];
+            src_line[2] = src_line[1];
+
+            if (y < height - 1)
+                src_line[2] += src_linesize;
+        }
+    }
+
+    return 0;
+}
+
+static int epx3_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    ThreadData *td = arg;
+    const AVFrame *in = td->in;
+    AVFrame *out = td->out;
+    const int slice_start = (in->height *  jobnr   ) / nb_jobs;
+    const int slice_end   = (in->height * (jobnr+1)) / nb_jobs;
+
+    for (int p = 0; p < 1; p++) {
+        const int width = in->width;
+        const int height = in->height;
+        const int src_linesize = in->linesize[p] / 4;
+        const int dst_linesize = out->linesize[p] / 4;
+        const uint32_t *src = (const uint32_t *)in->data[p];
+        uint32_t *dst = (uint32_t *)out->data[p];
+        const uint32_t *src_line[3];
+
+        src_line[0] = src + src_linesize * FFMAX(slice_start - 1, 0);
+        src_line[1] = src + src_linesize * slice_start;
+        src_line[2] = src + src_linesize * FFMIN(slice_start + 1, height-1);
+
+        for (int y = slice_start; y < slice_end; y++) {
+            uint32_t *dst_line[3];
+
+            dst_line[0] = dst + dst_linesize*3*y;
+            dst_line[1] = dst + dst_linesize*(3*y+1);
+            dst_line[2] = dst + dst_linesize*(3*y+2);
+
+            for (int x = 0; x < width; x++) {
+                uint32_t E0, E1, E2, E3, E4, E5, E6, E7, E8;
+                uint32_t A, B, C, D, E, F, G, H, I;
+
+                A = src_line[0][FFMAX(x-1, 0)];
+                B = src_line[0][x];
+                C = src_line[0][FFMIN(x+1, width - 1)];
+                D = src_line[1][FFMAX(x-1, 0)];
+                E = src_line[1][x];
+                F = src_line[1][FFMIN(x+1, width - 1)];
+                G = src_line[2][FFMAX(x-1, 0)];
+                H = src_line[2][x];
+                I = src_line[2][FFMIN(x+1, width - 1)];
+
+                if (B != H && D != F) {
+                    E0 = D == B ? D : E;
+                    E1 = (D == B && E != C) || (B == F && E != A) ? B : E;
+                    E2 = B == F ? F : E;
+                    E3 = (D == B && E != G) || (D == H && E != A) ? D : E;
+                    E4 = E;
+                    E5 = (B == F && E != I) || (H == F && E != C) ? F : E;
+                    E6 = D == H ? D : E;
+                    E7 = (D == H && E != I) || (H == F && E != G) ? H : E;
+                    E8 = H == F ? F : E;
+                } else {
+                    E0 = E;
+                    E1 = E;
+                    E2 = E;
+                    E3 = E;
+                    E4 = E;
+                    E5 = E;
+                    E6 = E;
+                    E7 = E;
+                    E8 = E;
+                }
+
+                dst_line[0][x*3]   = E0;
+                dst_line[0][x*3+1] = E1;
+                dst_line[0][x*3+2] = E2;
+                dst_line[1][x*3]   = E3;
+                dst_line[1][x*3+1] = E4;
+                dst_line[1][x*3+2] = E5;
+                dst_line[2][x*3]   = E6;
+                dst_line[2][x*3+1] = E7;
+                dst_line[2][x*3+2] = E8;
+            }
+
+            src_line[0] = src_line[1];
+            src_line[1] = src_line[2];
+            src_line[2] = src_line[1];
+
+            if (y < height - 1)
+                src_line[2] += src_linesize;
+        }
+    }
+
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    EPXContext *s = ctx->priv;
+    AVFilterLink *inlink = ctx->inputs[0];
+    const AVPixFmtDescriptor *desc;
+
+    desc = av_pix_fmt_desc_get(outlink->format);
+    if (!desc)
+        return AVERROR_BUG;
+
+    outlink->w = inlink->w * s->n;
+    outlink->h = inlink->h * s->n;
+
+    switch (s->n) {
+    case 2:
+        s->epx_slice = epx2_slice;
+        break;
+    case 3:
+        s->epx_slice = epx3_slice;
+        break;
+    }
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_RGBA, AV_PIX_FMT_BGRA, AV_PIX_FMT_ARGB, AV_PIX_FMT_ABGR,
+        AV_PIX_FMT_NONE,
+    };
+
+    AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
+    if (!fmts_list)
+        return AVERROR(ENOMEM);
+    return ff_set_common_formats(ctx, fmts_list);
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    EPXContext *s = ctx->priv;
+    ThreadData td;
+
+    AVFrame *out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+    if (!out) {
+        av_frame_free(&in);
+        return AVERROR(ENOMEM);
+    }
+
+    av_frame_copy_props(out, in);
+
+    td.in = in, td.out = out;
+    ctx->internal->execute(ctx, s->epx_slice, &td, NULL, FFMIN(inlink->h, ff_filter_get_nb_threads(ctx)));
+
+    av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+
+static const AVFilterPad inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_epx = {
+    .name          = "epx",
+    .description   = NULL_IF_CONFIG_SMALL("Scale the input using EPX algorithm."),
+    .inputs        = inputs,
+    .outputs       = outputs,
+    .query_formats = query_formats,
+    .priv_size     = sizeof(EPXContext),
+    .priv_class    = &epx_class,
+    .flags         = AVFILTER_FLAG_SLICE_THREADS,
+};