readpng: put image on center if it's too large

diff --git a/readpng.c b/readpng.c
index af6bd56..83936ae 100644 (file)
--- a/readpng.c
+++ b/readpng.c
@@ -68,23 +68,28 @@ int readpng(void *dest, const char *fname, readpng_what what, int req_w, int req
        {
                case READPNG_BG:
                {
-                       int height, width, h;
+                       int height, width, h, x_ofs = 0, y_ofs = 0;
                        unsigned short *dst = dest;
+
                        if (png_get_bit_depth(png_ptr, info_ptr) != 8)
                        {
                                lprintf(__FILE__ ": bg image uses %ibpc, needed 8bpc\n", png_get_bit_depth(png_ptr, info_ptr));
                                break;
                        }
                        width = png_get_image_width(png_ptr, info_ptr);
-                       if (width > req_w)
+                       if (width > req_w) {
+                               x_ofs = (width - req_w) / 2;
                                width = req_w;
+                       }
                        height = png_get_image_height(png_ptr, info_ptr);
-                       if (height > req_h)
+                       if (height > req_h) {
+                               y_ofs = (height - req_h) / 2;
                                height = req_h;
+                       }
 
                        for (h = 0; h < height; h++)
                        {
-                               unsigned char *src = row_ptr[h];
+                               unsigned char *src = row_ptr[h + y_ofs] + x_ofs * 3;
                                int len = width;
                                while (len--)
                                {