FFmpeg: Add image scaling function

CMakeLists.txt

@@ -556,7 +556,7 @@ if(USE_FFMPEG)
 	endif()
 	include_directories(AFTER ${FFMPEG_INCLUDE_DIRS} ${LIBAVCODEC_INCLUDE_DIRS} ${LIBAVFILTER_INCLUDE_DIRS} ${LIBAVFORMAT_INCLUDE_DIRS} ${LIBAVRESAMPLE_INCLUDE_DIRS} ${LIBAVUTIL_INCLUDE_DIRS} ${LIBSWRESAMPLE_INCLUDE_DIRS} ${LIBSWSCALE_INCLUDE_DIRS})
 	link_directories(${FFMPEG_LIBRARY_DIRS} ${LIBAVCODEC_LIBRARY_DIRS} ${LIBAVFILTER_LIBRARY_DIRS} ${LIBAVFORMAT_LIBRARY_DIRS} ${LIBAVRESAMPLE_LIBRARY_DIRS} ${LIBAVUTIL_LIBRARY_DIRS} ${LIBSWRESAMPLE_LIBRARY_DIRS} ${LIBSWSCALE_LIBRARY_DIRS})
-	list(APPEND FEATURE_SRC "${CMAKE_CURRENT_SOURCE_DIR}/src/feature/ffmpeg/ffmpeg-encoder.c" "${CMAKE_CURRENT_SOURCE_DIR}/src/feature/ffmpeg/ffmpeg-decoder.c")
+	list(APPEND FEATURE_SRC "${CMAKE_CURRENT_SOURCE_DIR}/src/feature/ffmpeg/ffmpeg-encoder.c" "${CMAKE_CURRENT_SOURCE_DIR}/src/feature/ffmpeg/ffmpeg-decoder.c" "${CMAKE_CURRENT_SOURCE_DIR}/src/feature/ffmpeg/ffmpeg-scale.c")
 	list(APPEND DEPENDENCY_LIB ${FFMPEG_LIBRARIES} ${LIBAVCODEC_LIBRARIES} ${LIBAVFILTER_LIBRARIES} ${LIBAVFORMAT_LIBRARIES} ${LIBAVRESAMPLE_LIBRARIES} ${LIBAVUTIL_LIBRARIES} ${LIBSWSCALE_LIBRARIES} ${LIBSWRESAMPLE_LIBRARIES})
 	if(WIN32 AND NOT DEFINED VCPKG_TARGET_TRIPLET)
 		list(APPEND DEPENDENCY_LIB bcrypt)

include/mgba/core/interface.h

@@ -164,6 +164,7 @@ enum mColorFormat {
 	mCOLOR_BGRA5  = 0x08000,
 	mCOLOR_RGB8   = 0x10000,
 	mCOLOR_BGR8   = 0x20000,
+	mCOLOR_L8     = 0x40000,
 
 	mCOLOR_ANY    = -1
 };

src/feature/ffmpeg/ffmpeg-common.h

@@ -10,6 +10,8 @@
 
 CXX_GUARD_START
 
+#include <mgba/core/interface.h>
+
 #include <libavformat/avformat.h>
 #include <libavcodec/version.h>
 
@@ -32,6 +34,54 @@ CXX_GUARD_START
 #define FFMPEG_USE_PACKET_UNREF
 #endif
 
+static inline enum AVPixelFormat mColorFormatToFFmpegPixFmt(enum mColorFormat format) {
+	switch (format) {
+#ifndef USE_LIBAV
+	case mCOLOR_XRGB8:
+		return AV_PIX_FMT_0RGB;
+	case mCOLOR_XBGR8:
+		return AV_PIX_FMT_0BGR;
+	case mCOLOR_RGBX8:
+		return AV_PIX_FMT_RGB0;
+	case mCOLOR_BGRX8:
+		return AV_PIX_FMT_BGR0;
+#else
+	case mCOLOR_XRGB8:
+		return AV_PIX_FMT_ARGB;
+	case mCOLOR_XBGR8:
+		return AV_PIX_FMT_ABGR;
+	case mCOLOR_RGBX8:
+		return AV_PIX_FMT_RGBA;
+	case mCOLOR_BGRX8:
+		return AV_PIX_FMT_BGRA;
+#endif
+	case mCOLOR_ARGB8:
+		return AV_PIX_FMT_ARGB;
+	case mCOLOR_ABGR8:
+		return AV_PIX_FMT_ABGR;
+	case mCOLOR_RGBA8:
+		return AV_PIX_FMT_RGBA;
+	case mCOLOR_BGRA8:
+		return AV_PIX_FMT_BGRA;
+	case mCOLOR_RGB5:
+		return AV_PIX_FMT_RGB555;
+	case mCOLOR_BGR5:
+		return AV_PIX_FMT_BGR555;
+	case mCOLOR_RGB565:
+		return AV_PIX_FMT_RGB565;
+	case mCOLOR_BGR565:
+		return AV_PIX_FMT_BGR565;
+	case mCOLOR_RGB8:
+		return AV_PIX_FMT_RGB24;
+	case mCOLOR_BGR8:
+		return AV_PIX_FMT_BGR24;
+	case mCOLOR_L8:
+		return AV_PIX_FMT_GRAY8;
+	default:
+		return AV_PIX_FMT_NONE;
+	}
+}
+
 CXX_GUARD_END
 
 #endif

src/feature/ffmpeg/ffmpeg-scale.c

@@ -0,0 +1,36 @@
+/* Copyright (c) 2013-2021 Jeffrey Pfau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "ffmpeg-scale.h"
+
+#include <libswscale/swscale.h>
+
+static const int _qualityToFlags[] = {
+	SWS_POINT,
+	SWS_FAST_BILINEAR,
+	SWS_BILINEAR,
+	SWS_BICUBIC,
+	SWS_LANCZOS,
+	SWS_SINC,
+};
+
+void FFmpegScale(const void* input, int iwidth, int iheight, unsigned istride,
+                 void* output, int owidth, int oheight, unsigned ostride,
+                 enum mColorFormat format, int quality) {
+	enum AVPixelFormat pixFormat = mColorFormatToFFmpegPixFmt(format);
+	int flags;
+	if (quality < 0) {
+		quality = 0;
+	} else if ((unsigned) quality >= sizeof(_qualityToFlags) / sizeof(_qualityToFlags[0])) {
+		quality = sizeof(_qualityToFlags) / sizeof(_qualityToFlags[0]) - 1;
+	}
+	flags = _qualityToFlags[quality];
+
+	struct SwsContext* scaleContext = sws_getContext(iwidth, iheight, pixFormat,
+	    owidth, oheight, pixFormat,
+	    flags, 0, 0, 0);
+	sws_scale(scaleContext, (const uint8_t* const*) &input, (const int*) &istride, 0, iheight, (uint8_t* const*) &output, (const int*) &ostride);
+	sws_freeContext(scaleContext);
+}

src/feature/ffmpeg/ffmpeg-scale.h

@@ -0,0 +1,21 @@
+/* Copyright (c) 2013-2021 Jeffrey Pfau
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef FFMPEG_SCALE
+#define FFMPEG_SCALE
+
+#include <mgba-util/common.h>
+
+CXX_GUARD_START
+
+#include "feature/ffmpeg/ffmpeg-common.h"
+
+void FFmpegScale(const void* input, int iwidth, int iheight, unsigned istride,
+                 void* output, int owidth, int oheight, unsigned ostride,
+                 enum mColorFormat format, int quality);
+
+CXX_GUARD_END
+
+#endif