Avoid creation of unnecessary image bufs (at alt-text to img switch)

This is the first of a patch series for image code bugs that have
severe impact on performance.

With these testing files:

1imgA.html  =  <img src="maj00s.png" alt="img1">
2imgSA.html  = <img src="maj00s.png" alt="img1">
               <img src="maj00s.png" alt="img12">
3imgSA.html  = <img src="maj00s.png" alt="img1">
               <img src="maj00s.png" alt="img12">
               <img src="maj00s.png" alt="img123">

2imgA.html  =  <img src="maj00s.png" alt="img1">
               <img src="maj21s.png" alt="img12">
3imgA.html  =  <img src="maj00s.png" alt="img1">
               <img src="maj21s.png" alt="img12">
               <img src="c10s.png" alt="img123">

This are the results:

.------------------------------------------------------------------.
|imgbufs     |         No patch         |         Patched #1       |
|            | first time | upon reload | first time | upon reload |
|-------------------------------------------------------------------
|1imgA.html  |     2      |     1       |     1      |      1      |
|2imgSA.html |     3      |     2       |     1      |      2      |
|3imgSA.html |     4      |     3       |     1      |      3      |
|-------------------------------------------------------------------
|2imgA.html  |     4      |     2       |     2      |      2      |
|3imgA.html  |     6      |     3       |     3      |      3      |
'------------------------------------------------------------------'

1 files changed, 4 insertions, 2 deletions

diff --git a/src/image.cc b/src/image.cc
index 9915023a..97270eef 100644
--- a/src/image.cc
+++ b/src/image.cc
@@ -106,9 +106,11 @@ void a_Image_set_parms(DilloImage *Image, void *v_imgbuf, DilloUrl *url,
                        int version, uint_t width, uint_t height,
                        DilloImgType type)
 {
-   _MSG("a_Image_set_parms: width=%d height=%d\n", width, height);
+   _MSG("a_Image_set_parms: width=%d height=%d iw=%d ih=%d\n",
+        width, height, Image->width, Image->height);
 
-   bool resize = (Image->width != width || Image->height != height);
+   /* Resize from 0,0 to width,height */
+   bool resize = true;
    I2IR(Image)->setBuffer((Imgbuf*)v_imgbuf, resize);
 
    if (!Image->BitVec)