From 697c1cfa9d67413138349a28380f65be8c6b464d Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Sat, 23 Sep 2017 12:33:36 -0700
Subject: [PATCH] Util: Add alpha versions of PNG functions

---
 include/mgba-util/png-io.h |  2 ++
 src/util/png-io.c          | 69 ++++++++++++++++++++++++++++++++------
 2 files changed, 60 insertions(+), 11 deletions(-)

diff --git a/include/mgba-util/png-io.h b/include/mgba-util/png-io.h
index 983992856..7156d67cb 100644
--- a/include/mgba-util/png-io.h
+++ b/include/mgba-util/png-io.h
@@ -26,9 +26,11 @@ enum {
 
 png_structp PNGWriteOpen(struct VFile* source);
 png_infop PNGWriteHeader(png_structp png, unsigned width, unsigned height);
+png_infop PNGWriteHeaderA(png_structp png, unsigned width, unsigned height);
 png_infop PNGWriteHeader8(png_structp png, unsigned width, unsigned height);
 bool PNGWritePalette(png_structp png, png_infop info, const uint32_t* palette, unsigned entries);
 bool PNGWritePixels(png_structp png, unsigned width, unsigned height, unsigned stride, const void* pixels);
+bool PNGWritePixelsA(png_structp png, unsigned width, unsigned height, unsigned stride, const void* pixels);
 bool PNGWritePixels8(png_structp png, unsigned width, unsigned height, unsigned stride, const void* pixels);
 bool PNGWriteCustomChunk(png_structp png, const char* name, size_t size, void* data);
 void PNGWriteClose(png_structp png, png_infop info);
diff --git a/src/util/png-io.c b/src/util/png-io.c
index 0cb721b83..24d301676 100644
--- a/src/util/png-io.c
+++ b/src/util/png-io.c
@@ -38,7 +38,7 @@ png_structp PNGWriteOpen(struct VFile* source) {
 	return png;
 }
 
-png_infop PNGWriteHeader(png_structp png, unsigned width, unsigned height) {
+static png_infop _pngWriteHeader(png_structp png, unsigned width, unsigned height, int type) {
 	png_infop info = png_create_info_struct(png);
 	if (!info) {
 		return 0;
@@ -46,21 +46,21 @@ png_infop PNGWriteHeader(png_structp png, unsigned width, unsigned height) {
 	if (setjmp(png_jmpbuf(png))) {
 		return 0;
 	}
-	png_set_IHDR(png, info, width, height, 8, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+	png_set_IHDR(png, info, width, height, 8, type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 	png_write_info(png, info);
 	return info;
 }
 
+png_infop PNGWriteHeader(png_structp png, unsigned width, unsigned height) {
+	return _pngWriteHeader(png, width, height, PNG_COLOR_TYPE_RGB);
+}
+
+png_infop PNGWriteHeaderA(png_structp png, unsigned width, unsigned height) {
+	return _pngWriteHeader(png, width, height, PNG_COLOR_TYPE_RGB_ALPHA);
+}
+
 png_infop PNGWriteHeader8(png_structp png, unsigned width, unsigned height) {
-	png_infop info = png_create_info_struct(png);
-	if (!info) {
-		return 0;
-	}
-	if (setjmp(png_jmpbuf(png))) {
-		return 0;
-	}
-	png_set_IHDR(png, info, width, height, 8, PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
-	return info;
+	return _pngWriteHeader(png, width, height, PNG_COLOR_TYPE_PALETTE);
 }
 
 bool PNGWritePalette(png_structp png, png_infop info, const uint32_t* palette, unsigned entries) {
@@ -128,6 +128,53 @@ bool PNGWritePixels(png_structp png, unsigned width, unsigned height, unsigned s
 	return true;
 }
 
+bool PNGWritePixelsA(png_structp png, unsigned width, unsigned height, unsigned stride, const void* pixels) {
+	png_bytep row = malloc(sizeof(png_byte) * width * 4);
+	if (!row) {
+		return false;
+	}
+	const png_byte* pixelData = pixels;
+	if (setjmp(png_jmpbuf(png))) {
+		free(row);
+		return false;
+	}
+	unsigned i;
+	for (i = 0; i < height; ++i) {
+		unsigned x;
+		for (x = 0; x < width; ++x) {
+#ifdef COLOR_16_BIT
+			uint16_t c = ((uint16_t*) pixelData)[stride * i + x];
+#ifdef COLOR_5_6_5
+			row[x * 4] = (c >> 8) & 0xF8;
+			row[x * 4 + 1] = (c >> 3) & 0xFC;
+			row[x * 4 + 2] = (c << 3) & 0xF8;
+			row[x * 4 + 3] = 0xFF;
+#else
+			row[x * 4] = (c >> 7) & 0xF8;
+			row[x * 4 + 1] = (c >> 2) & 0xF8;
+			row[x * 4 + 2] = (c << 3) & 0xF8;
+			row[x * 4 + 3] = (c >> 15) * 0xFF;
+#endif
+#else
+#ifdef __BIG_ENDIAN__
+			row[x * 4] = pixelData[stride * i * 4 + x * 4 + 3];
+			row[x * 4 + 1] = pixelData[stride * i * 4 + x * 4 + 2];
+			row[x * 4 + 2] = pixelData[stride * i * 4 + x * 4 + 1];
+			row[x * 4 + 3] = pixelData[stride * i * 4 + x * 4];
+#else
+			row[x * 4] = pixelData[stride * i * 4 + x * 4];
+			row[x * 4 + 1] = pixelData[stride * i * 4 + x * 4 + 1];
+			row[x * 4 + 2] = pixelData[stride * i * 4 + x * 4 + 2];
+			row[x * 4 + 3] = pixelData[stride * i * 4 + x * 4 + 3];
+#endif
+#endif
+		}
+		png_write_row(png, row);
+	}
+	free(row);
+	return true;
+}
+
 bool PNGWritePixels8(png_structp png, unsigned width, unsigned height, unsigned stride, const void* pixels) {
 	UNUSED(width);
 	const png_byte* pixelData = pixels;