[sdl] libpng screenshot support

Makefile

@@ -6,13 +6,14 @@ BUILDDIR = build
 CC = gcc
 CFLAGS = -g -O2 -flto -std=c11 -Wall
 LDFLAGS = -g -O2
-LIBS = -lGL -lSDL2 -lSDL2main
+LIBS = -lGL -lSDL2 -lSDL2main -lpng
 TARGET = $(BUILDDIR)/zeta86
 
 OBJS =	$(OBJDIR)/8x14.o \
 	\
 	$(OBJDIR)/cpu.o \
 	$(OBJDIR)/zzt.o \
+	$(OBJDIR)/asset_loader.o \
 	$(OBJDIR)/audio_stream.o \
 	\
 	$(OBJDIR)/posix_vfs.o \

src/config.h

@@ -31,6 +31,7 @@
 #define BLINK_TOGGLE_DURATION_MS 267
 #define ENABLE_SCREENSHOTS
 #define USE_GETOPT
+#define USE_LIBPNG
 #define USE_OPENGL
 // #define USE_OPENGL_ES /* GLES 1.1, not production ready */
 

src/frontend_sdl.c

@@ -760,7 +760,13 @@ int main(int argc, char **argv) {
 						else if (sdl_is_blink_phase(zeta_time_ms())) sflags |= RENDER_BLINK_PHASE;
 
 						while ((++i) <= 9999) {
+#ifdef USE_LIBPNG
+							int stype = SCREENSHOT_TYPE_PNG;
+							snprintf(filename, 23, "screen%d.png", i);
+#else
+							int stype = SCREENSHOT_TYPE_BMP;
 							snprintf(filename, 23, "screen%d.bmp", i);
+#endif
 							file = fopen(filename, "rb");
 							if (!file) {
 								file = fopen(filename, "wb");
@@ -769,7 +775,7 @@ int main(int argc, char **argv) {
 									break;
 								}
 								if (write_screenshot(
-									file, SCREENSHOT_TYPE_BMP,
+									file, stype,
 									swidth, sflags,
 									zzt_get_ram(), charset_update_data,
 									8, charset_char_height,

src/screenshot_writer.c

@@ -19,6 +19,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include "screenshot_writer.h"
 
 #define POS_MUL (scr_width <= 40 ? 2 : 1)
@@ -35,6 +36,30 @@ static void fput32le(FILE *output, int i) {
 	fputc(((i >> 24) & 0xFF), output);
 }
 
+#ifdef USE_LIBPNG
+#include <png.h>
+
+static int write_screenshot_png(FILE *output, u8 *buffer, u32 *palette, int flags, int width, int height) {
+	png_image image;
+	u8 colormap[48];
+
+	memset(&image, 0, sizeof(image));
+	image.version = PNG_IMAGE_VERSION;
+	image.width = width;
+	image.height = height;
+	image.format = PNG_FORMAT_RGB_COLORMAP;
+	image.colormap_entries = 16;
+
+	for (int i = 0; i < 16; i++) {
+		colormap[i*3 + 0] = palette[i] >> 16;
+		colormap[i*3 + 1] = palette[i] >> 8;
+		colormap[i*3 + 2] = palette[i] >> 0;
+	}
+
+	return png_image_write_to_stdio(&image, output, 0, buffer, 0, colormap) > 0;
+}
+#endif
+
 static int write_screenshot_bmp(FILE *output, u8 *buffer, u32 *palette, int flags, int width, int height) {
 	int bmp_size = 54 + (4*16) + (width * height / 2);
 
@@ -82,7 +107,7 @@ static int write_screenshot_bmp(FILE *output, u8 *buffer, u32 *palette, int flag
 int write_screenshot(FILE *output, int type, int scr_width, int flags, u8 *ram, u8 *charset, int char_width, int char_height, u32 *palette) {
 	void *buffer;
 
-	int paletted = (type == SCREENSHOT_TYPE_BMP);
+	int paletted = (type == SCREENSHOT_TYPE_BMP || type == SCREENSHOT_TYPE_PNG);
 
 	buffer = malloc(char_width * char_height * scr_width * POS_MUL * 25 * (paletted ? sizeof(u8) : sizeof(u32)));
 	if (buffer == NULL) {
@@ -97,10 +122,18 @@ int write_screenshot(FILE *output, int type, int scr_width, int flags, u8 *ram,
 
 	int result;
 
-	if (type == SCREENSHOT_TYPE_BMP) {
-		result = write_screenshot_bmp(output, (u8*) buffer, palette, flags, char_width * scr_width * POS_MUL, char_height * 25);
-	} else {
-		result = -1;
+	switch (type) {
+		case SCREENSHOT_TYPE_BMP:
+			result = write_screenshot_bmp(output, (u8*) buffer, palette, flags, char_width * scr_width * POS_MUL, char_height * 25);
+			break;
+#ifdef USE_LIBPNG
+		case SCREENSHOT_TYPE_PNG:
+			result = write_screenshot_png(output, (u8*) buffer, palette, flags, char_width * scr_width * POS_MUL, char_height * 25);
+			break;
+#endif
+		default:
+			result = -1;
+			break;
 	}
 
 	free(buffer);

src/screenshot_writer.h

@@ -21,9 +21,11 @@
 #define __SCREENSHOT_RENDER_H__
 
 #include "types.h"
+#include "config.h"
 #include "render_software.h"
 
 #define SCREENSHOT_TYPE_BMP 0
+#define SCREENSHOT_TYPE_PNG 1
 
 USER_FUNCTION
 int write_screenshot(FILE *output, int type, int scr_width, int flags, u8 *ram, u8 *charset, int char_width, int char_height, u32 *palette);

zeta_sdl.sh

@@ -5,4 +5,4 @@ gcc -o build/zeta86 -g -O2 -std=c18 -Wall \
   src/frontend_sdl.c src/zzt.c src/cpu.c \
   src/screenshot_writer.c src/render_software.c \
   src/asset_loader.c \
-  -lGL -lSDL2 -lSDL2main
+  -lGL -lSDL2 -lSDL2main -lpng