+/*
+ -----------------------------------------------------------------------------
+ ZoomPixmap
+
+ Important note: The scaling code currently only supports scaling down the
+ image by a power of 2 -- scaling up is currently not supported at all!
+ -----------------------------------------------------------------------------
+*/
+
+void ZoomPixmap(Display *display, GC gc, Pixmap src_pixmap, Pixmap dst_pixmap,
+ int src_width, int src_height,
+ int dst_width, int dst_height)
+{
+ XImage *src_ximage, *dst_ximage;
+ byte *src_ptr, *dst_ptr;
+ int bits_per_pixel;
+ int bytes_per_pixel;
+ int x, y, i;
+ int zoom_factor = src_width / dst_width; /* currently very limited! */
+ int row_skip, col_skip;
+
+ /* copy source pixmap to temporary image */
+ src_ximage = XGetImage(display, src_pixmap, 0, 0,
+ src_width, src_height, AllPlanes, ZPixmap);
+
+ bits_per_pixel = src_ximage->bits_per_pixel;
+ bytes_per_pixel = (bits_per_pixel + 7) / 8;
+
+ dst_ximage = XCreateImage(display, visual, src_ximage->depth, ZPixmap,
+ 0, NULL, dst_width, dst_height,
+ 8, dst_width * bytes_per_pixel);
+ dst_ximage->data =
+ checked_malloc(dst_width * dst_height * bytes_per_pixel);
+ dst_ximage->byte_order = src_ximage->byte_order;
+
+ src_ptr = (byte *)src_ximage->data;
+ dst_ptr = (byte *)dst_ximage->data;
+
+ col_skip = (zoom_factor - 1) * bytes_per_pixel;
+ row_skip = col_skip * src_width;
+
+ /* scale image down by scaling factor 'zoom_factor' */
+ for (y=0; y < src_height; y += zoom_factor, src_ptr += row_skip)
+ for (x=0; x < src_width; x += zoom_factor, src_ptr += col_skip)
+ for (i=0; i<bytes_per_pixel; i++)
+ *dst_ptr++ = *src_ptr++;
+
+ /* copy scaled image to destination pixmap */
+ XPutImage(display, dst_pixmap, gc, dst_ximage, 0, 0, 0, 0,
+ MIN(src_width, dst_width), MIN(src_height, dst_height));
+
+ /* free temporary images */
+ XDestroyImage(src_ximage);
+ XDestroyImage(dst_ximage);
+}
+