Initial revision

wrlib/scale.c

@@ -0,0 +1,143 @@
+/* scale.c - image scaling
+ * 
+ *  Raster graphics library
+ * 
+ *  Copyright (c) 1997 Alfredo K. Kojima
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Library General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *  
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Library General Public License for more details.
+ *  
+ *  You should have received a copy of the GNU Library General Public
+ *  License along with this library; if not, write to the Free
+ *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <X11/Xlib.h>
+
+#include <assert.h>
+
+#include "wraster.h"
+
+
+/*
+ *----------------------------------------------------------------------
+ * RScaleImage--
+ * 	Creates a scaled copy of an image.
+ * 
+ * Returns:
+ * 	The new scaled image.
+ * 
+ *---------------------------------------------------------------------- 
+ */
+RImage*
+RScaleImage(RImage *image, unsigned new_width, unsigned new_height)
+{
+    int ox;
+    int px, py;
+    register int x, y, t;
+    int dx, dy;
+    unsigned char *sr, *sg, *sb, *sa;
+    unsigned char *dr, *dg, *db, *da;
+    RImage *img;
+
+    assert(new_width >= 0 && new_height >= 0);
+
+    if (new_width == image->width && new_height == image->height)
+	return RCloneImage(image);
+
+    img = RCreateImage(new_width, new_height, image->data[3]!=NULL);
+    
+    if (!img)
+      return NULL;
+
+    /* fixed point math idea taken from Imlib by 
+     * Carsten Haitzler (Rasterman) */
+    dx = (image->width<<16)/new_width;
+    dy = (image->height<<16)/new_height;
+
+    py = 0;
+    
+    dr = img->data[0];
+    dg = img->data[1];
+    db = img->data[2];
+    da = img->data[3];
+
+    if (image->data[3]!=NULL) {
+	int ot;
+	ot = -1;
+	for (y=0; y<new_height; y++) {
+	    t = image->width*(py>>16);
+
+	    sr = image->data[0]+t;
+	    sg = image->data[1]+t;
+	    sb = image->data[2]+t;
+	    sa = image->data[3]+t;
+
+	    ot = t;
+	    ox = 0;
+	    px = 0;
+	    for (x=0; x<new_width; x++) {
+		px += dx;
+
+		*(dr++) = *sr;
+		*(dg++) = *sg;
+		*(db++) = *sb;
+		*(da++) = *sa;
+		
+		t = (px - ox)>>16;
+		ox += t<<16;
+		    
+		sr += t;
+		sg += t;
+		sb += t;
+		sa += t;
+	    }
+	    py += dy;
+	}
+    } else {
+	int ot;
+	ot = -1;
+	for (y=0; y<new_height; y++) {
+	    t = image->width*(py>>16);
+
+	    sr = image->data[0]+t;
+	    sg = image->data[1]+t;
+	    sb = image->data[2]+t;
+	    
+	    ot = t;
+	    ox = 0;
+	    px = 0;
+	    for (x=0; x<new_width; x++) {
+		px += dx;
+		
+		*(dr++) = *sr;
+		*(dg++) = *sg;
+		*(db++) = *sb;
+		
+		t = (px-ox)>>16;
+		ox += t<<16;
+		
+		sr += t;
+		sg += t;
+		sb += t;
+	    }
+	    py += dy;
+	}
+    }
+    
+    return img;
+}
+