From b325f796c0c691986620f58e7d8104bc16f79d9e Mon Sep 17 00:00:00 2001
From: Andinus <andinus@nand.sh>
Date: Sun, 10 Oct 2021 20:01:00 +0530
Subject: Implement Bresenham's Algorithm

---
 src/algorithms/line-drawing/Bresenham.svelte | 172 ++++++++++++++++++++++++++-
 src/algorithms/line-drawing/DDA.svelte       |   1 -
 2 files changed, 171 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/algorithms/line-drawing/Bresenham.svelte b/src/algorithms/line-drawing/Bresenham.svelte
index d2f81af..e3eaff1 100644
--- a/src/algorithms/line-drawing/Bresenham.svelte
+++ b/src/algorithms/line-drawing/Bresenham.svelte
@@ -1 +1,171 @@
-<p>Bresenham</p>
+<svelte:head>
+  <script src="./plotly/plotly.min.js" on:load={plotlyLoaded}></script>
+</svelte:head>
+<script>
+  let solved = false;
+  let invalidInput = false;
+
+  let plotlyReady = false;
+  const plotlyLoaded = () => {
+    plotlyReady = true;
+    solve();
+  }
+
+  let x0 = 0, y0 = 0, x1 = 4, y1 = 4;
+  let dx, dy, step;
+
+  let x_inc, y_inc;
+  let x_axis = [], y_axis = [], p_vals = [];
+
+  function solve() {
+    dx = Math.abs(x1 - x0);
+    dy = Math.abs(y1 - y0);
+
+    // Early return if slope is not between 0 - 1.
+    if (dy > dx) {
+      invalidInput = true;
+      return;
+    } else {
+      invalidInput = false;
+    }
+
+    let p = (2 * dy) - dx;
+    p_vals.push(p);
+
+    step = 2 * (dy - dx);
+
+    // Build the x axis and y axis.
+    x_axis = [x0,];
+    y_axis = [y0,];
+
+    for (let idx = 0; idx < dx; idx++) {
+        // x_axis.at(-1) doesn't work for some reason.
+        x_axis.push(x_axis[x_axis.length - 1] + 1);
+        if (p < 0) {
+            y_axis.push(y_axis[y_axis.length - 1]);
+            p += 2 * dy;
+        } else {
+            y_axis.push(y_axis[y_axis.length - 1] + 1);
+            p += step;
+        }
+      p_vals.push(p);
+    }
+
+    // Plot the chart.
+    if (plotlyReady)
+      Plotly.newPlot('algoChart', [{
+        x: x_axis,
+        y: y_axis,
+        type: 'lines',
+        name: 'Bresenham'
+      }]);
+
+    solved = true;
+  }
+</script>
+
+<h2>Bresenham</h2>
+<form class="points">
+  {#if invalidInput === true}
+    <p class="note">
+      Slope must be between 0 to 1.
+    </p>
+  {/if}
+  <label for="x0">x0: </label>
+  <input type="number" id="x0" name="x0" on:change={solve} bind:value={x0}>&nbsp;
+  <label for="y0">y0: </label>
+  <input type="number" id="y0" name="y0" on:change={solve} bind:value={y0}>
+  <br>
+  <label for="x1">x1: </label>
+  <input type="number" id="x1" name="x1" on:change={solve} bind:value={x1}>&nbsp;
+  <label for="y1">y1: </label>
+  <input type="number" id="y1" name="y1" on:change={solve} bind:value={y1}>
+  <br>
+  <button type="button" on:click={solve}>Solve</button>
+</form>
+
+{#if solved === true}
+  <hr>
+  <h3>Solution</h3>
+
+  <table>
+    <thead>
+      <tr>
+        <th>&nbsp;</th>
+        <th>Value</th>
+      </tr>
+    </thead>
+    <tbody>
+        <tr>
+          <td>dx = <code>|x1 - x0|</code></td>
+          <td>{dx}</td>
+        </tr>
+        <tr>
+          <td>dy = <code>|y1 - y0|</code></td>
+          <td>{dy}</td>
+        </tr>
+        <tr>
+          <td>step = <code>|2 * (dy - dx)|</code></td>
+          <td>{step}</td>
+        </tr>
+        <tr>
+          <td><code>2 * dy</code></td>
+          <td>{2 * dy}</td>
+        </tr>
+        <tr>
+          <td>p<sub>0</sub></td>
+          <td>{p_vals[0]}</td>
+        </tr>
+    </tbody>
+  </table>
+
+  <details>
+    <summary>
+      Table
+    </summary>
+    <table>
+      <thead>
+        <tr>
+          <th>Iteration (k)</th>
+          <th>P<sub>k</sub></th>
+          <th>x<sub>k + 1</sub></th>
+          <th>y<sub>k + 1</sub></th>
+        </tr>
+      </thead>
+
+      <tbody>
+        {#each x_axis as _, i}
+          <tr>
+            <td>{i}</td>
+            <td>{p_vals[i]}</td>
+            <td>{x_axis[i]}</td>
+            <td>{y_axis[i]}</td>
+          </tr>
+        {/each}
+      </tbody>
+    </table>
+  </details>
+
+  <h3>Graph</h3>
+  {#if plotlyReady === false}
+    <p class="note">
+      Cannot plot graph: Plotly is not ready.
+    </p>
+  {/if}
+{/if}
+<div id="algoChart"></div>
+
+<style>
+  hr { color: var(--bg-hl-alt-intense); }
+  button {
+    margin: .8em;
+    padding: 0.4em 1.2em;
+    width: 100%;
+  }
+  details {
+    border: 1px solid var(--bg-alt);
+    border-radius: 4px;
+    padding: 0.8em;
+    margin: 1em;
+  }
+</style>
diff --git a/src/algorithms/line-drawing/DDA.svelte b/src/algorithms/line-drawing/DDA.svelte
index b759cdc..c9f62a0 100644
--- a/src/algorithms/line-drawing/DDA.svelte
+++ b/src/algorithms/line-drawing/DDA.svelte
@@ -124,7 +124,6 @@
 
   <h3>Graph</h3>
   {#if plotlyReady === false}
-
     <p class="note">
       Cannot plot graph: Plotly is not ready.
     </p>
-- 
cgit 1.4.1-2-gfad0