Initial PNG support (courtesy of lodepng).

arm9/Makefile

@@ -6,7 +6,7 @@ SOURCE := source
 BUILD  := build
 
 SUBARCH := -D$(PROCESSOR) -mcpu=arm946e-s -mtune=arm946e-s -mfloat-abi=soft -mthumb
-INCDIRS := source source/common source/filesys source/crypto source/fatfs source/nand source/virtual source/game source/gamecart source/quicklz source/qrcodegen source/system source/utils
+INCDIRS := source source/common source/filesys source/crypto source/fatfs source/nand source/virtual source/game source/gamecart source/lodepng source/quicklz source/qrcodegen source/system source/utils
 INCLUDE := $(foreach dir,$(INCDIRS),-I"$(shell pwd)/$(dir)")
 
 ASFLAGS += $(SUBARCH) $(INCLUDE)

arm9/source/system/png.c

@@ -0,0 +1,32 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include "lodepng.h"
+#include "png.h"
+
+#include "ui.h"
+
+u8 *PNG_Decompress(const u8 *png, size_t png_len, size_t *w, size_t *h)
+{
+	u8 *img;
+	u32 res;
+	size_t w_, h_;
+
+	res = lodepng_decode24(&img, &w_, &h_, png, png_len);
+	if (res) {
+		ShowPrompt(false, "PNG error: %s", lodepng_error_text(res));
+		return NULL;
+	}
+
+	// maybe process in batches of 3 pixels / 12 bytes at a time?
+	for (size_t i = 0; i < (w_ * h_ * 3); i += 3) {
+		u8 c = img[i];
+		img[i] = img[i + 2];
+		img[i + 2] = c;
+	}
+
+	if (w) *w = w_;
+	if (h) *h = h_;
+
+	return img;
+}

arm9/source/system/png.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <stdint.h>
+#include "common.h"
+#include "lodepng/lodepng.h"
+
+u8 *PNG_Decompress(const u8 *png, size_t png_len, size_t *w, size_t *h);