fix HTML problems related to pandoc and markdown image notation

Improve `make clobber` for `2004/anonymous`.

Instead of using this markdown element to embed an image:

```
![alt text](filename.png "Title")
```

Use a "img" HTML element with "alt", "alt", "width" and "length"
attributes:

```
<img src="filename.png"
 alt="describe the filename.png image for someone who cannot view it"
 width=PIXEL_WIDTH height=PIXEL_HEIGHT>
```

This was performed for:

```
2004/anonymous/index.html
2005/boutines/index.html
2011/goren/index.html
2012/vik/index.html
2013/birken/index.html
2013/cable1/index.html
2013/cable3/index.html
2013/hou/doc/example.html
2013/hou/index.html
2020/ferguson1/chocolate-cake.html
```

In the case of `2013/cable1/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2013/hou/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2020/ferguson1/chocolate-cake.html` we reduce the displayed
image size by a factor for 4.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

Run `make www` to perform the above.

2013/hou/README.md

@@ -39,11 +39,17 @@ you leave the program running overnight to see what happens. If however you do
 not have all night :-) then the following JPEG files should show you what
 happens with some of the invocations above:
 
-![./hou BIG - Luna](luna.jpg)
+<img src="luna.jpg"
+ alt="artificial image showing a room lit by light from a window"
+ width=640 height=480>
 
-![./hou old_default.scene - Old default](old_default.jpg)
+<img src="old_default.jpg"
+ alt="artificial image showing IOCCC 2013 in a room with stars on the floor and double helix in the backgrond"
+ width=640 height=480>
 
-![./hou otherroom.scene - Other room](otherroom.jpg)
+<img src="otherroom.jpg"
+ alt="artificial image the background double helix"
+ width=320 height=240>
 
 This program does not terminate by itself: you must kill `hou` (but not Qiming
 Hou :-) ) in order to end the program.

2013/hou/doc/example.html

@@ -271,9 +271,12 @@ cell content in variable <code>C</code>. To fill it with material <code>i</code>
 <code>C</code>. To fill it with volume <code>i</code>, well, return <code>i</code>. To leave it empty, return
 <code>C=0</code>.</p>
 <p>Before starting to build a scene, it’s better to have a draft sketch handy
-first. Something like <img src="draft.png" alt="Draft sketch" />. Sometimes it’s hard to
-imagine where something should go without the sketch. And you don’t have to
-stick to your sketch :)</p>
+first. Something like:</p>
+<p><img src="draft.png"
+ alt="image of the draft sketch of a room with a window"
+ width=513 height=487></p>
+<p>Sometimes it’s hard to imagine where something should go without the sketch.
+And you don’t have to stick to your sketch :)</p>
 <p>What motivated my default scene: it was the full moon’s day (a national holiday)
 in China and my parents were planning to renovate their apartment. I rendered
 the image to tell my mom how ridiculous her starry-sky wall paper would look
@@ -303,9 +306,11 @@ renderer would assemble the colors into an image.</p>
 <p>Remember the function <code>5</code>? Here it comes. The first two “random” numbers have
 special meaning and must specify a point on the image plane <code>[0,1)x[0,1)</code>.
 You’re supposed to transform the image plane to the 3D space, choose a point for
-the camera, and shoot a ray from the camera point to the image plane point, see
-<img src="camera.png" alt="Camera convention" />. The camera point goes to <code>(U,V,W)</code>, and the
-ray direction vector (image plane point - camera point) is <code>(X,Y,Z)</code>. For the
+the camera, and shoot a ray from the camera point to the image plane point, see:</p>
+<p><img src="camera.png"
+ alt="image of a sketch showing a light ray from an object (person) thru an image plane pixel to a camera viewpoint"
+ width=935 height=632></p>
+<p>.. and the ray direction vector (image plane point - camera point) is <code>(X,Y,Z)</code>. For the
 coordinate space, volume 0 is scaled up 64x here to <code>(0,0,0)-(4096,4096,4096)</code>.</p>
 <p>For a basic camera shader example, check <a href="../otherroom.scene">otherroom.scene</a>.</p>
 <p>If any ray goes out of volume 0, the renderer crashes. Make sure it doesn’t
@@ -395,7 +400,9 @@ the incoming direction and the surface normal. It’s called importance sampling
 because here the probability of each outgoing direction has to be proportional
 to the reflected light strength (i.e., the <code>BRDF</code>) on that direction. For a
 diffuse surface, sample the upper hemisphere with a probability proportional to
-the cosine of the outgoing angle, see <img src="cosine.png" alt="Cosine sampling" />.</p>
+the cosine of the outgoing angle, see <img src="cosine.png"
+ alt="image of a sketch of a ray a angle theta from the vertical normal with cosine theta below it"
+ width=935 height=632>.</p>
 <p>The incoming direction is in <code>(X,Y,Z)</code> and the hit point is <code>(U,V,W)</code>. The
 outgoing direction is returned in, where else, <code>(X,Y,Z)</code>.</p>
 <p>The surface normal is provided in variables <code>S</code> and <code>T</code>. Since the geometry is

2013/hou/doc/example.md

@@ -191,9 +191,14 @@ cell content in variable `C`. To fill it with material `i`, return `64+i` in
 `C=0`.
 
 Before starting to build a scene, it's better to have a draft sketch handy
-first. Something like ![ Draft sketch ](draft.png). Sometimes it's hard to
-imagine where something should go without the sketch. And you don't have to
-stick to your sketch :)
+first. Something like:
+
+<img src="draft.png"
+ alt="image of the draft sketch of a room with a window"
+ width=513 height=487>
+
+Sometimes it's hard to imagine where something should go without the sketch.
+And you don't have to stick to your sketch :)
 
 What motivated my default scene: it was the full moon's day (a national holiday)
 in China and my parents were planning to renovate their apartment. I rendered
@@ -233,9 +238,13 @@ renderer would assemble the colors into an image.
 Remember the function `5`? Here it comes. The first two "random" numbers have
 special meaning and must specify a point on the image plane `[0,1)x[0,1)`.
 You're supposed to transform the image plane to the 3D space, choose a point for
-the camera, and shoot a ray from the camera point to the image plane point, see
-![ Camera convention ](camera.png). The camera point goes to `(U,V,W)`, and the
-ray direction vector (image plane point - camera point) is `(X,Y,Z)`. For the
+the camera, and shoot a ray from the camera point to the image plane point, see:
+
+<img src="camera.png"
+ alt="image of a sketch showing a light ray from an object (person) thru an image plane pixel to a camera viewpoint"
+ width=935 height=632>
+
+.. and the ray direction vector (image plane point - camera point) is `(X,Y,Z)`. For the
 coordinate space, volume 0 is scaled up 64x here to `(0,0,0)-(4096,4096,4096)`.
 
 For a basic camera shader example, check [otherroom.scene](../otherroom.scene).
@@ -349,7 +358,9 @@ the incoming direction and the surface normal. It's called importance sampling,
 because here the probability of each outgoing direction has to be proportional
 to the reflected light strength (i.e., the `BRDF`) on that direction. For a
 diffuse surface, sample the upper hemisphere with a probability proportional to
-the cosine of the outgoing angle, see ![ Cosine sampling ](cosine.png).
+the cosine of the outgoing angle, see <img src="cosine.png"
+ alt="image of a sketch of a ray a angle theta from the vertical normal with cosine theta below it"
+ width=935 height=632>.
 
 The incoming direction is in `(X,Y,Z)` and the hit point is `(U,V,W)`. The
 outgoing direction is returned in, where else, `(X,Y,Z)`.

2013/hou/index.html

@@ -170,18 +170,15 @@ every so often reopen the file, to see how it changes. The author suggests that
 you leave the program running overnight to see what happens. If however you do
 not have all night :-) then the following JPEG files should show you what
 happens with some of the invocations above:</p>
-<figure>
-<img src="luna.jpg" alt="./hou BIG - Luna" />
-<figcaption aria-hidden="true">./hou BIG - Luna</figcaption>
-</figure>
-<figure>
-<img src="old_default.jpg" alt="./hou old_default.scene - Old default" />
-<figcaption aria-hidden="true">./hou old_default.scene - Old default</figcaption>
-</figure>
-<figure>
-<img src="otherroom.jpg" alt="./hou otherroom.scene - Other room" />
-<figcaption aria-hidden="true">./hou otherroom.scene - Other room</figcaption>
-</figure>
+<p><img src="luna.jpg"
+ alt="artificial image showing a room lit by light from a window"
+ width=640 height=480></p>
+<p><img src="old_default.jpg"
+ alt="artificial image showing IOCCC 2013 in a room with stars on the floor and double helix in the backgrond"
+ width=640 height=480></p>
+<p><img src="otherroom.jpg"
+ alt="artificial image the background double helix"
+ width=320 height=240></p>
 <p>This program does not terminate by itself: you must kill <code>hou</code> (but not Qiming
 Hou :-) ) in order to end the program.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>