Oops, make sure image values are treated as *unsigned*, for TXF_INTENSITY.

src/textures.c

@@ -118,16 +118,18 @@ int txbind( Texture *tx, int *enabled )
 
     if(wanted) {
 	static float black[4] = {0,0,0,0};
-	char *txdata = tx->data;
+	unsigned char *txdata = (unsigned char *)tx->data;
 	int channels = tx->channels;
 
 	if((tx->flags&TXF_INTENSITY) && (channels == 1 || channels == 3)) {
 	    int npix = tx->xsize * tx->ysize;
 	    int k;
-	    char *ip, *op;
+	    unsigned char *ip, *op;
 	    channels++;
-	    txdata = (char *)malloc( npix * channels );
-	    k = npix, ip = tx->data, op = txdata;
+	    txdata = (unsigned char *)malloc( npix * channels );
+	    k = npix;
+	    ip = (unsigned char *)tx->data;
+	    op = txdata;
 	    switch(channels) {
 	    case 2:
 		do {
@@ -156,7 +158,7 @@ int txbind( Texture *tx, int *enabled )
 		    GL_UNSIGNED_BYTE,
 		    txdata);
 
-	if(txdata != tx->data)
+	if(txdata != (unsigned char *)tx->data)
 	    free(txdata);
 
 	glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR,