--- a/src/libgfx.h	Fri Aug 18 15:27:36 2017 +0300
+++ b/src/libgfx.h	Fri Aug 18 17:32:19 2017 +0300
@@ -66,7 +66,9 @@
 
 typedef struct
 {
-    int scaleX, scaleY, nplanes, format;
+    int format;
+    int scaleX, scaleY;
+    int nplanes, bpp;
     BOOL interleave, paletted;
 } DMImageSpec;
 
@@ -78,8 +80,8 @@
     int  (*probe)(const Uint8 *buf, const size_t len);
     int  (*read)(const char *filename, DMImage **pimg);
     int  (*readFILE)(FILE *fp, DMImage **pimg);
-    int  (*write)(const char *filename, DMImage *pimg, DMImageSpec *spec);
-    int  (*writeFILE)(FILE *fp, DMImage *pimg, DMImageSpec *spec);
+    int  (*write)(const char *filename, DMImage *pimg, const DMImageSpec *spec);
+    int  (*writeFILE)(FILE *fp, DMImage *pimg, const DMImageSpec *spec);
 } DMImageFormat;
 
 
@@ -106,19 +108,19 @@
 int dmWriteImageData(DMImage *img, void *cbdata, int (*writeRowCB)(void *, Uint8 *, size_t), const DMImageSpec *spec);
 
 int dmWriteIFFMasterRAWPalette(FILE *fp, DMImage *img, int ncolors, const char *indent, const char *type);
-int dmWriteRAWImageFILE(FILE *fp, DMImage *img, DMImageSpec *spec);
-int dmWriteRAWImage(const char *filename, DMImage *img, DMImageSpec *spec);
+int dmWriteRAWImageFILE(FILE *fp, DMImage *img, const DMImageSpec *spec);
+int dmWriteRAWImage(const char *filename, DMImage *img, const DMImageSpec *spec);
 
-int dmWritePPMImageFILE(FILE *fp, DMImage *img, DMImageSpec *spec);
-int dmWritePPMImage(const char *filename, DMImage *img, DMImageSpec *spec);
+int dmWritePPMImageFILE(FILE *fp, DMImage *img, const DMImageSpec *spec);
+int dmWritePPMImage(const char *filename, DMImage *img, const DMImageSpec *spec);
 
 #ifdef DM_USE_LIBPNG
-int dmWritePNGImageFILE(FILE *fp, DMImage *img, DMImageSpec *spec);
-int dmWritePNGImage(const char *filename, DMImage *img, DMImageSpec *spec);
+int dmWritePNGImageFILE(FILE *fp, DMImage *img, const DMImageSpec *spec);
+int dmWritePNGImage(const char *filename, DMImage *img, const DMImageSpec *spec);
 #endif
 
-int dmWritePCXImageFILE(FILE *fp, DMImage *img, DMImageSpec *spec);
-int dmWritePCXImage(const char *filename, DMImage *img, DMImageSpec *spec);
+int dmWritePCXImageFILE(FILE *fp, DMImage *img, const DMImageSpec *spec);
+int dmWritePCXImage(const char *filename, DMImage *img, const DMImageSpec *spec);
 int dmReadPCXImageFILE(FILE *fp, DMImage **pimg);
 int dmReadPCXImage(const char *filename, DMImage **pimg);