diff --git a/modules/Gpx/Gpx.c b/modules/Gpx/Gpx.c
index 729f2e3..da7085e 100644
--- a/modules/Gpx/Gpx.c
+++ b/modules/Gpx/Gpx.c
@@ -69,33 +69,17 @@ static int find_null_surface() {
 }
 
 static void sf_free_one(int no) {
-	surface_t *s;
-	if (no == 0) return;
-	
-	s = suf[no];
-	if (s == NULL) return;
-	
-	if (s->pixel) free(s->pixel);
-	if (s->alpha) free(s->alpha);
-	free(s);
-	
+	if (no == 0 || !suf[no]) return;
+	sf_free(suf[no]);
 	suf[no] = NULL;
 	pre_freesurfno = no;
 }
 
 static void sf_free_all() {
-	int i;
-	surface_t *s;
-	
-	for (i = 1; i < MAX_SURFACE; i++) {
-		if (suf[i] == NULL) continue;
-		s = suf[i];
-		if (s->pixel) free(s->pixel);
-		if (s->alpha) free(s->alpha);
-		free(s);
+	for (int i = 1; i < MAX_SURFACE; i++) {
+		sf_free(suf[i]);
 		suf[i] = NULL;
 	}
-	
 	pre_freesurfno = 1;
 }
 
diff --git a/modules/NIGHTDLL/sactcg.c b/modules/NIGHTDLL/sactcg.c
index a90e28d..495791e 100644
--- a/modules/NIGHTDLL/sactcg.c
+++ b/modules/NIGHTDLL/sactcg.c
@@ -26,6 +26,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <SDL.h>
 
 #include "portab.h"
 #include "nact.h"
diff --git a/modules/NIGHTDLL/sactcg_stretch.c b/modules/NIGHTDLL/sactcg_stretch.c
index 9f16f10..b1eea7e 100644
--- a/modules/NIGHTDLL/sactcg_stretch.c
+++ b/modules/NIGHTDLL/sactcg_stretch.c
@@ -14,7 +14,10 @@ static surface_t *stretch(surface_t *src, int dw, int dh, int mirror) {
 	dst->bytes_per_pixel = src->bytes_per_pixel;
 	
 	if (src->pixel) {
-		dst->pixel = malloc(dh * dst->bytes_per_line);
+		dst->sdl_surface = SDL_CreateRGBSurfaceWithFormat(0, dw, dh, src->depth, src->sdl_surface->format->format);
+		dst->pixel = dst->sdl_surface->pixels;
+		dst->bytes_per_line = dst->sdl_surface->pitch;
+		dst->bytes_per_pixel = dst->sdl_surface->format->BytesPerPixel;
 	}
 	if (src->alpha) {
 		dst->alpha = malloc(dw * dh);
diff --git a/modules/SACT/sactcg.c b/modules/SACT/sactcg.c
index 5bd3b41..a948969 100644
--- a/modules/SACT/sactcg.c
+++ b/modules/SACT/sactcg.c
@@ -26,6 +26,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <SDL.h>
 
 #include "portab.h"
 #include "nact.h"
diff --git a/modules/SACT/sactcg_stretch.c b/modules/SACT/sactcg_stretch.c
index 310fae6..a3272c6 100644
--- a/modules/SACT/sactcg_stretch.c
+++ b/modules/SACT/sactcg_stretch.c
@@ -14,7 +14,10 @@ static surface_t *stretch(surface_t *src, int dw, int dh, int mirror) {
 	dst->bytes_per_pixel = src->bytes_per_pixel;
 	
 	if (src->pixel) {
-		dst->pixel = malloc(dh * dst->bytes_per_line);
+		dst->sdl_surface = SDL_CreateRGBSurfaceWithFormat(0, dw, dh, src->depth, src->sdl_surface->format->format);
+		dst->pixel = dst->sdl_surface->pixels;
+		dst->bytes_per_line = dst->sdl_surface->pitch;
+		dst->bytes_per_pixel = dst->sdl_surface->format->BytesPerPixel;
 	}
 	if (src->alpha) {
 		dst->alpha = malloc(dw * dh);
diff --git a/modules/lib/surface.c b/modules/lib/surface.c
index b9a9714..16363df 100644
--- a/modules/lib/surface.c
+++ b/modules/lib/surface.c
@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <SDL.h>
 
 #include "portab.h"
 #include "surface.h"
@@ -19,26 +20,26 @@ static surface_t *create(int width, int height, int depth, bool has_pixel, bool
 	s->depth = depth;
 	
 	if (has_pixel) {
+		uint32_t format = 0;
 		switch (s->depth) {
 		case 8:
-			s->pixel = calloc(width * (height +1), sizeof(uint8_t));
-			s->bytes_per_line = width;
-			s->bytes_per_pixel = 1;
+			format = SDL_PIXELFORMAT_INDEX8;
 			break;
 		case 16:
-			s->pixel = calloc(width * (height +1) * 2, sizeof(uint8_t));
-			s->bytes_per_line = width * 2;
-			s->bytes_per_pixel = 2;
+			format = SDL_PIXELFORMAT_RGB565;
 			break;
 		case 24:
 		case 32:
-			s->pixel = calloc(width * (height +1) * 4, sizeof(uint8_t));
-			s->bytes_per_line = width * 4;
-			s->bytes_per_pixel = 4;
+			format = SDL_PIXELFORMAT_RGB888;
+			depth = 32;
 			break;
 		default:
-			WARNING("depth %d is not supported", s->depth);
+			SYSERROR("depth %d is not supported", s->depth);
 		}
+		s->sdl_surface = SDL_CreateRGBSurfaceWithFormat(0, width, height, depth, format);
+		s->pixel = s->sdl_surface->pixels;
+		s->bytes_per_line = s->sdl_surface->pitch;
+		s->bytes_per_pixel = s->sdl_surface->format->BytesPerPixel;
 	}
 	
 	if (has_alpha) {
@@ -87,7 +88,7 @@ surface_t *sf_create_pixel(int width, int height, int depth) {
  */
 void sf_free(surface_t *s) {
 	if (s == NULL) return;
-	if (s->pixel) free(s->pixel);
+	if (s->sdl_surface) SDL_FreeSurface(s->sdl_surface);
 	if (s->alpha) free(s->alpha);
 	free(s);
 }
@@ -107,9 +108,10 @@ surface_t *sf_dup(surface_t *in) {
 	memcpy(sf, in, sizeof(surface_t));
 	
 	if (in->pixel) {
-		len = sf->bytes_per_line * sf->height;
-		sf->pixel = malloc(sizeof(uint8_t) * (len + sf->bytes_per_line));
-		memcpy(sf->pixel, in->pixel, len);
+		sf->sdl_surface = SDL_ConvertSurface(in->sdl_surface, in->sdl_surface->format, 0);
+		sf->pixel = sf->sdl_surface->pixels;
+		sf->bytes_per_line = sf->sdl_surface->pitch;
+		sf->bytes_per_pixel = sf->sdl_surface->format->BytesPerPixel;
 	}
 	
 	if (in->alpha) {
@@ -148,39 +150,3 @@ void sf_copyall(surface_t *dst, surface_t *src) {
 		memcpy(dst->pixel, src->pixel, len);
 	}
 }
-
-/**
- * surface の複製
- * @param in: 複製もと
- * @param copypixel: pixelをコピーするか
- * @param copyalpha: alpha pixel をコピーするか
- * @return: 複製した surface
- */
-surface_t *sf_dup2(surface_t *in, bool copypixel, bool copyalpha) {
-	surface_t *sf;
-	int len;
-	
-	if (in == NULL) return NULL;
-	
-	sf = malloc(sizeof(surface_t));
-	memcpy(sf, in, sizeof(surface_t));
-	
-	if (in->pixel) {
-		len = sf->bytes_per_line * sf->height;
-		sf->pixel = malloc(sizeof(uint8_t) * (len + sf->bytes_per_line));
-		if (copypixel) {
-			memcpy(sf->pixel, in->pixel, len);
-		}
-	}
-	
-	if (in->alpha) {
-		len = sf->width * sf->height;
-		sf->alpha = malloc(sizeof(uint8_t) * (len + sf->width));
-		if (copyalpha) {
-			memcpy(sf->alpha, in->alpha, len);
-		}
-	}
-	
-	return sf;
-}
-
diff --git a/modules/lib/surface.h b/modules/lib/surface.h
index 241101d..440a793 100644
--- a/modules/lib/surface.h
+++ b/modules/lib/surface.h
@@ -11,7 +11,6 @@ extern surface_t *sf_create_alpha(int width, int height);
 extern surface_t *sf_create_pixel(int width, int height, int depth);
 extern void       sf_free(surface_t *s);
 extern surface_t *sf_dup(surface_t *in);
-extern surface_t *sf_dup2(surface_t *in, bool copypixel, bool copyalpha);
 extern void       sf_copyall(surface_t *dst, surface_t *src);
 
 
diff --git a/src/ags.h b/src/ags.h
index ddb136f..4719bde 100644
--- a/src/ags.h
+++ b/src/ags.h
@@ -45,6 +45,8 @@
 #define CURSOR_UPARROW  12
 #define CURSOR_WAIT     13
 
+struct SDL_Surface;
+
 /* RGB <-> alpha plane copy type */
 typedef enum {
 	FROM_16H,
@@ -69,6 +71,8 @@ struct agsurface {
 	
 	uint8_t *pixel; /* pixel data (can be NULL) */
 	uint8_t *alpha; /* alpha pixel data (can be NULL) */
+
+	struct SDL_Surface *sdl_surface;
 };
 typedef struct agsurface agsurface_t;
 
diff --git a/src/sdl_core.h b/src/sdl_core.h
index cf78264..8701b54 100644
--- a/src/sdl_core.h
+++ b/src/sdl_core.h
@@ -48,7 +48,7 @@ extern bool sdl_isFullscreen(void);
 extern void sdl_raiseWindow(void);
 extern agsurface_t *sdl_getDIB(void);
 extern void sdl_setIntegerScaling(bool enable);
-extern SDL_Surface *sdl_createSurfaceView(agsurface_t *s, int x, int y, int w, int h);
+extern SDL_Surface *sdl_createSurfaceView(SDL_Surface *sf, int x, int y, int w, int h);
 
 /* 画面更新 */
 extern void sdl_updateArea(MyRectangle *src, MyPoint *dst);
diff --git a/src/sdl_effect.c b/src/sdl_effect.c
index 66b1547..fd629bf 100644
--- a/src/sdl_effect.c
+++ b/src/sdl_effect.c
@@ -137,7 +137,7 @@ static EffectTexture *create_effect_texture(agsurface_t *as, int x, int y, int w
 		t->tx = sdl_texture;
 		t->rect = (SDL_Rect){ x, y, w, h };
 	} else {
-		SDL_Surface *sf = sdl_createSurfaceView(as, x, y, w, h);
+		SDL_Surface *sf = sdl_createSurfaceView(as->sdl_surface, x, y, w, h);
 		t->tx = SDL_CreateTextureFromSurface(sdl_renderer, sf);
 		SDL_FreeSurface(sf);
 		t->rect = (SDL_Rect){ 0, 0, w, h };
diff --git a/src/sdl_video.c b/src/sdl_video.c
index 14ed297..8e09397 100644
--- a/src/sdl_video.c
+++ b/src/sdl_video.c
@@ -198,6 +198,7 @@ static void makeDIB(int width, int height, int depth) {
 	sdl_dibinfo->width  = width;
 	sdl_dibinfo->height = height;
 	sdl_dibinfo->alpha  = NULL;
+	sdl_dibinfo->sdl_surface = sdl_dib;
 	
 	image_setdepth(sdl_dibinfo->depth);
 }
@@ -222,19 +223,14 @@ agsurface_t *sdl_getDIB(void) {
 	return sdl_dibinfo;
 }
 
-SDL_Surface *sdl_createSurfaceView(agsurface_t *s, int x, int y, int w, int h) {
-	if (s == sdl_dibinfo) {
-		uint8_t *pixels = sdl_dib->pixels;
-		pixels += y * sdl_dib->pitch + x * sdl_dib->format->BytesPerPixel;
-		SDL_Surface *view = SDL_CreateRGBSurfaceWithFormatFrom(
-			pixels, w, h, sdl_dib->format->BitsPerPixel, sdl_dib->pitch, sdl_dib->format->format);
-		if (sdl_dib->format->palette)
-			SDL_SetSurfacePalette(view, sdl_dib->format->palette);
-		return view;
-	} else {
-		uint8_t *pixels = s->pixel + y * s->bytes_per_line + x * s->bytes_per_pixel;
-		return SDL_CreateRGBSurfaceFrom(pixels, w, h, s->depth, s->bytes_per_line, 0, 0, 0, 0);
-	}
+SDL_Surface *sdl_createSurfaceView(SDL_Surface *sf, int x, int y, int w, int h) {
+	uint8_t *pixels = sf->pixels;
+	pixels += y * sf->pitch + x * sf->format->BytesPerPixel;
+	SDL_Surface *view = SDL_CreateRGBSurfaceWithFormatFrom(
+		pixels, w, h, sf->format->BitsPerPixel, sf->pitch, sf->format->format);
+	if (sf->format->palette)
+		SDL_SetSurfacePalette(view, sf->format->palette);
+	return view;
 }
 
 /* AutoRepeat の設定 */
@@ -303,7 +299,7 @@ void sdl_setIntegerScaling(bool enable) {
 
 bool EMSCRIPTEN_KEEPALIVE save_screenshot(const char* path) {
 	SDL_Rect *r = &nact->ags.view_area;
-	SDL_Surface *view = sdl_createSurfaceView(sdl_dibinfo, r->x, r->y, r->w, r->h);
+	SDL_Surface *view = sdl_createSurfaceView(sdl_dib, r->x, r->y, r->w, r->h);
 	bool ok = SDL_SaveBMP(view, path) == 0;
 	SDL_FreeSurface(view);
 	return ok;