lavfi: add colorkey_opencl filter

This is a direct port of the CPU filter.

Signed-off-by: Jarek Samic <cldfire3@gmail.com>
Signed-off-by: Mark Thompson <sw@jkqxz.net>

configure

@@ -3412,6 +3412,7 @@ bm3d_filter_select="dct"
 boxblur_filter_deps="gpl"
 boxblur_opencl_filter_deps="opencl gpl"
 bs2b_filter_deps="libbs2b"
+colorkey_opencl_filter_deps="opencl"
 colormatrix_filter_deps="gpl"
 convolution_opencl_filter_deps="opencl"
 convolve_filter_deps="avcodec"

doc/filters.texi

@@ -19103,6 +19103,39 @@ Apply erosion filter with threshold0 set to 30, threshold1 set 40, threshold2 se
 @end example
 @end itemize
 
+@section colorkey_opencl
+RGB colorspace color keying.
+
+The filter accepts the following options:
+
+@table @option
+@item color
+The color which will be replaced with transparency.
+
+@item similarity
+Similarity percentage with the key color.
+
+0.01 matches only the exact key color, while 1.0 matches everything.
+
+@item blend
+Blend percentage.
+
+0.0 makes pixels either fully transparent, or not transparent at all.
+
+Higher values result in semi-transparent pixels, with a higher transparency
+the more similar the pixels color is to the key color.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Make every semi-green pixel in the input transparent with some slight blending:
+@example
+-i INPUT -vf "hwupload, colorkey_opencl=green:0.3:0.1, hwdownload" OUTPUT
+@end example
+@end itemize
+
 @section overlay_opencl
 
 Overlay one video on top of another.

libavfilter/Makefile

@@ -176,6 +176,8 @@ OBJS-$(CONFIG_CODECVIEW_FILTER)              += vf_codecview.o
 OBJS-$(CONFIG_COLORBALANCE_FILTER)           += vf_colorbalance.o
 OBJS-$(CONFIG_COLORCHANNELMIXER_FILTER)      += vf_colorchannelmixer.o
 OBJS-$(CONFIG_COLORKEY_FILTER)               += vf_colorkey.o
+OBJS-$(CONFIG_COLORKEY_OPENCL_FILTER)        += vf_colorkey_opencl.o opencl.o \
+                                                opencl/colorkey.o
 OBJS-$(CONFIG_COLORLEVELS_FILTER)            += vf_colorlevels.o
 OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COLORSPACE_FILTER)             += vf_colorspace.o colorspace.o colorspacedsp.o

libavfilter/allfilters.c

@@ -165,6 +165,7 @@ extern AVFilter ff_vf_codecview;
 extern AVFilter ff_vf_colorbalance;
 extern AVFilter ff_vf_colorchannelmixer;
 extern AVFilter ff_vf_colorkey;
+extern AVFilter ff_vf_colorkey_opencl;
 extern AVFilter ff_vf_colorlevels;
 extern AVFilter ff_vf_colormatrix;
 extern AVFilter ff_vf_colorspace;

libavfilter/opencl/colorkey.cl

@@ -0,0 +1,49 @@
+/*
+ * 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
+ */
+
+const sampler_t sampler = CLK_NORMALIZED_COORDS_FALSE |
+                          CLK_FILTER_NEAREST;
+
+__kernel void colorkey_blend(
+    __read_only  image2d_t src,
+    __write_only image2d_t dst,
+    float4 colorkey_rgba,
+    float similarity,
+    float blend
+) {
+    int2 loc = (int2)(get_global_id(0), get_global_id(1));
+    float4 pixel = read_imagef(src, sampler, loc);
+    float diff = distance(pixel.xyz, colorkey_rgba.xyz);
+
+    pixel.s3 = clamp((diff - similarity) / blend, 0.0f, 1.0f);
+    write_imagef(dst, loc, pixel);
+}
+
+__kernel void colorkey(
+    __read_only  image2d_t src,
+    __write_only image2d_t dst,
+    float4 colorkey_rgba,
+    float similarity
+) {
+    int2 loc = (int2)(get_global_id(0), get_global_id(1));
+    float4 pixel = read_imagef(src, sampler, loc);
+    float diff = distance(pixel.xyz, colorkey_rgba.xyz);
+
+    pixel.s3 = (diff > similarity) ? 1.0f : 0.0f;
+    write_imagef(dst, loc, pixel);
+}

libavfilter/opencl_source.h

@@ -20,6 +20,7 @@
 #define AVFILTER_OPENCL_SOURCE_H
 
 extern const char *ff_opencl_source_avgblur;
+extern const char *ff_opencl_source_colorkey;
 extern const char *ff_opencl_source_colorspace_common;
 extern const char *ff_opencl_source_convolution;
 extern const char *ff_opencl_source_neighbor;

libavfilter/vf_colorkey_opencl.c

@@ -0,0 +1,244 @@
+/*
+ * 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/imgutils.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "opencl.h"
+#include "opencl_source.h"
+#include "video.h"
+
+typedef struct ColorkeyOpenCLContext {
+    OpenCLFilterContext ocf;
+    // Whether or not the above `OpenCLFilterContext` has been initialized
+    int initialized;
+
+    cl_command_queue command_queue;
+    cl_kernel kernel_colorkey;
+
+    // The color we are supposed to replace with transparency
+    uint8_t colorkey_rgba[4];
+    // Stored as a normalized float for passing to the OpenCL kernel
+    cl_float4 colorkey_rgba_float;
+    // Similarity percentage compared to `colorkey_rgba`, ranging from `0.01` to `1.0`
+    // where `0.01` matches only the key color and `1.0` matches all colors
+    float similarity;
+    // Blending percentage where `0.0` results in fully transparent pixels, `1.0` results
+    // in fully opaque pixels, and numbers in between result in transparency that varies
+    // based on the similarity to the key color
+    float blend;
+} ColorkeyOpenCLContext;
+
+static int colorkey_opencl_init(AVFilterContext *avctx)
+{
+    ColorkeyOpenCLContext *ctx = avctx->priv;
+    cl_int cle;
+    int err;
+
+    err = ff_opencl_filter_load_program(avctx, &ff_opencl_source_colorkey, 1);
+    if (err < 0)
+        goto fail;
+
+    ctx->command_queue = clCreateCommandQueue(
+        ctx->ocf.hwctx->context,
+        ctx->ocf.hwctx->device_id,
+        0,
+        &cle
+    );
+
+    CL_FAIL_ON_ERROR(AVERROR(EIO), "Failed to create OpenCL command queue %d.\n", cle);
+
+    if (ctx->blend > 0.0001) {
+        ctx->kernel_colorkey = clCreateKernel(ctx->ocf.program, "colorkey_blend", &cle);
+        CL_FAIL_ON_ERROR(AVERROR(EIO), "Failed to create colorkey_blend kernel: %d.\n", cle);
+    } else {
+        ctx->kernel_colorkey = clCreateKernel(ctx->ocf.program, "colorkey", &cle);
+        CL_FAIL_ON_ERROR(AVERROR(EIO), "Failed to create colorkey kernel: %d.\n", cle);
+    }
+
+    for (int i = 0; i < 4; ++i) {
+        ctx->colorkey_rgba_float.s[i] = (float)ctx->colorkey_rgba[i] / 255.0;
+    }
+
+    ctx->initialized = 1;
+    return 0;
+
+fail:
+    if (ctx->command_queue)
+        clReleaseCommandQueue(ctx->command_queue);
+    if (ctx->kernel_colorkey)
+        clReleaseKernel(ctx->kernel_colorkey);
+    return err;
+}
+
+static int filter_frame(AVFilterLink *link, AVFrame *input_frame)
+{
+    AVFilterContext *avctx = link->dst;
+    AVFilterLink *outlink = avctx->outputs[0];
+    ColorkeyOpenCLContext *colorkey_ctx = avctx->priv;
+    AVFrame *output_frame = NULL;
+    int err;
+    cl_int cle;
+    size_t global_work[2];
+    cl_mem src, dst;
+
+    if (!input_frame->hw_frames_ctx)
+        return AVERROR(EINVAL);
+
+    if (!colorkey_ctx->initialized) {
+        AVHWFramesContext *input_frames_ctx =
+            (AVHWFramesContext*)input_frame->hw_frames_ctx->data;
+        int fmt = input_frames_ctx->sw_format;
+
+        // Make sure the input is a format we support
+        if (fmt != AV_PIX_FMT_ARGB &&
+            fmt != AV_PIX_FMT_RGBA &&
+            fmt != AV_PIX_FMT_ABGR &&
+            fmt != AV_PIX_FMT_BGRA
+        ) {
+            av_log(avctx, AV_LOG_ERROR, "unsupported (non-RGB) format in colorkey_opencl.\n");
+            err = AVERROR(ENOSYS);
+            goto fail;
+        }
+
+        err = colorkey_opencl_init(avctx);
+        if (err < 0)
+            goto fail;
+    }
+
+    // This filter only operates on RGB data and we know that will be on the first plane
+    src = (cl_mem)input_frame->data[0];
+    output_frame = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+    if (!output_frame) {
+        err = AVERROR(ENOMEM);
+        goto fail;
+    }
+    dst = (cl_mem)output_frame->data[0];
+
+    CL_SET_KERNEL_ARG(colorkey_ctx->kernel_colorkey, 0, cl_mem, &src);
+    CL_SET_KERNEL_ARG(colorkey_ctx->kernel_colorkey, 1, cl_mem, &dst);
+    CL_SET_KERNEL_ARG(colorkey_ctx->kernel_colorkey, 2, cl_float4, &colorkey_ctx->colorkey_rgba_float);
+    CL_SET_KERNEL_ARG(colorkey_ctx->kernel_colorkey, 3, float, &colorkey_ctx->similarity);
+    if (colorkey_ctx->blend > 0.0001) {
+        CL_SET_KERNEL_ARG(colorkey_ctx->kernel_colorkey, 4, float, &colorkey_ctx->blend);
+    }
+
+    err = ff_opencl_filter_work_size_from_image(avctx, global_work, input_frame, 0, 0);
+    if (err < 0)
+        goto fail;
+
+    cle = clEnqueueNDRangeKernel(
+        colorkey_ctx->command_queue,
+        colorkey_ctx->kernel_colorkey,
+        2,
+        NULL,
+        global_work,
+        NULL,
+        0,
+        NULL,
+        NULL
+    );
+
+    CL_FAIL_ON_ERROR(AVERROR(EIO), "Failed to enqueue colorkey kernel: %d.\n", cle);
+
+    // Run queued kernel
+    cle = clFinish(colorkey_ctx->command_queue);
+    CL_FAIL_ON_ERROR(AVERROR(EIO), "Failed to finish command queue: %d.\n", cle);
+
+    err = av_frame_copy_props(output_frame, input_frame);
+    if (err < 0)
+        goto fail;
+
+    av_frame_free(&input_frame);
+
+    return ff_filter_frame(outlink, output_frame);
+
+fail:
+    clFinish(colorkey_ctx->command_queue);
+    av_frame_free(&input_frame);
+    av_frame_free(&output_frame);
+    return err;
+}
+
+static av_cold void colorkey_opencl_uninit(AVFilterContext *avctx)
+{
+    ColorkeyOpenCLContext *ctx = avctx->priv;
+    cl_int cle;
+
+    if (ctx->kernel_colorkey) {
+        cle = clReleaseKernel(ctx->kernel_colorkey);
+        if (cle != CL_SUCCESS)
+            av_log(avctx, AV_LOG_ERROR, "Failed to release "
+                   "kernel: %d.\n", cle);
+    }
+
+    if (ctx->command_queue) {
+        cle = clReleaseCommandQueue(ctx->command_queue);
+        if (cle != CL_SUCCESS)
+            av_log(avctx, AV_LOG_ERROR, "Failed to release "
+                   "command queue: %d.\n", cle);
+    }
+
+    ff_opencl_filter_uninit(avctx);
+}
+
+static const AVFilterPad colorkey_opencl_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+        .config_props = &ff_opencl_filter_config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad colorkey_opencl_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .config_props = &ff_opencl_filter_config_output,
+    },
+    { NULL }
+};
+
+#define OFFSET(x) offsetof(ColorkeyOpenCLContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption colorkey_opencl_options[] = {
+    { "color", "set the colorkey key color", OFFSET(colorkey_rgba), AV_OPT_TYPE_COLOR, { .str = "black" }, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "similarity", "set the colorkey similarity value", OFFSET(similarity), AV_OPT_TYPE_FLOAT, { .dbl = 0.01 }, 0.01, 1.0, FLAGS },
+    { "blend", "set the colorkey key blend value", OFFSET(blend), AV_OPT_TYPE_FLOAT, { .dbl = 0.0 }, 0.0, 1.0, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(colorkey_opencl);
+
+AVFilter ff_vf_colorkey_opencl = {
+    .name           = "colorkey_opencl",
+    .description    = NULL_IF_CONFIG_SMALL("Turns a certain color into transparency. Operates on RGB colors."),
+    .priv_size      = sizeof(ColorkeyOpenCLContext),
+    .priv_class     = &colorkey_opencl_class,
+    .init           = &ff_opencl_filter_init,
+    .uninit         = &colorkey_opencl_uninit,
+    .query_formats  = &ff_opencl_filter_query_formats,
+    .inputs         = colorkey_opencl_inputs,
+    .outputs        = colorkey_opencl_outputs,
+    .flags_internal = FF_FILTER_FLAG_HWFRAME_AWARE
+};