From 2b1a3323a8736dabd66a3a6a98d266699ea09d9d Mon Sep 17 00:00:00 2001
From: Dominic Masters <dominic@domsplace.com>
Date: Mon, 16 Feb 2026 12:00:55 -0600
Subject: [PATCH] Tileset creator done

---
 tools/tileset-creator.html | 566 +++++++++++++++++++++++++------------
 1 file changed, 388 insertions(+), 178 deletions(-)

diff --git a/tools/tileset-creator.html b/tools/tileset-creator.html
index ce8ba12..883240c 100644
--- a/tools/tileset-creator.html
+++ b/tools/tileset-creator.html
@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Dusk Tools / Tileset Creator</title>
-    
+
     <style type="text/css">
       * {
         box-sizing: border-box;
@@ -13,7 +13,7 @@
       body {
         font-size: 16px;
       }
-      
+
       canvas {
         image-rendering: pixelated;
       }
@@ -31,20 +31,52 @@
     <div>
       <h2>Tileset Settings</h2>
       <div>
-        <label>Tile Width:</label>
-        <input type="number" value="8" data-tile-width min="1" step="1" />
+        <button data-load-tileset>Load Tileset</button>
+      </div>
+
+      <div>
+        Define tile count by:
+        <div>
+          <label>
+            Tile Size
+            <input type="radio" name="define-by" value="size" checked />
+          </label>
+
+          <label>
+            Tile Count
+            <input type="radio" name="define-by" value="count" />
+          </label>
+        </div>
+      </div>
+
+      <div data-tile-sizes>
+        <div>
+          <label>Tile Width:</label>
+          <input type="number" value="8" data-tile-width min="1" step="1" />
+        </div>
+        <div>
+          <label>Tile Height:</label>
+          <input type="number" value="8" data-tile-height min="1" step="1" />
+        </div>
+      </div>
+      <div data-tile-counts style="display: none;">
+        <div>
+          <label>Column Count:</label>
+          <input type="number" value="10" data-column-count min="1" step="1" />
+        </div>
+        <div>
+          <label>Row Count:</label>
+          <input type="number" value="10" data-row-count min="1" step="1" />
+        </div>
+      </div>
+
+      <div>
+        <label>Unused Space on Right of Texture:</label>
+        <input type="number" value="0" data-right min="0" step="1" />
       </div>
       <div>
-        <label>Tile Height:</label>
-        <input type="number" value="8" data-tile-height min="1" step="1" />
-      </div>
-      <div>
-        <label>Column Count:</label>
-        <input type="number" value="10" data-column-count min="1" step="1" />
-      </div>
-      <div>
-        <label>Row Count:</label>
-        <input type="number" value="10" data-row-count min="1" step="1" />
+        <label>Unused Space on Bottom of Texture:</label>
+        <input type="number" value="0" data-bottom min="0" step="1" />
       </div>
     </div>
 
@@ -61,28 +93,34 @@
         </label>
       </div>
       <div>
-      <label>
-        Preview Background:
-        <button data-page-bg-white>White</button>
-        <button data-page-bg-transparent>Black</button>
-        <button data-page-bg-checkerboard>Checkerboard</button>
-        <button data-page-bg-magenta>Magenta</button>
-        <button data-page-bg-blue>Blue</button>
-        <button data-page-bg-green>Green</button>
-      </label>
-    </div>
-    <div>
-      <canvas data-output-preview style="border:1px solid black;"></canvas>
-    </div>
-    <div>
-      <textarea data-output-information rows="15" style="width: 500px;"></textarea>
-    </div>
-    <div>
-      <button data-tileset-download>Download Tileset</button>
+        <label>
+          Preview Background:
+          <button data-page-bg-white>White</button>
+          <button data-page-bg-transparent>Black</button>
+          <button data-page-bg-checkerboard>Checkerboard</button>
+          <button data-page-bg-magenta>Magenta</button>
+          <button data-page-bg-blue>Blue</button>
+          <button data-page-bg-green>Green</button>
+        </label>
+      </div>
+      <div>
+        <canvas data-output-preview style="border:1px solid black;"></canvas>
+      </div>
+      <div>
+        <textarea data-output-information rows="15" style="width: 500px;"></textarea>
+      </div>
+      <div>
+        <button data-tileset-download>Download Tileset</button>
+      </div>
     </div>
   </body>
 
   <script type="text/javascript">
+    // Element selectors
+    const elDefineBySize = document.querySelector('input[name="define-by"][value="size"]');
+    const elDefineByCount = document.querySelector('input[name="define-by"][value="count"]');
+    const elTileSizes = document.querySelector('[data-tile-sizes]');
+    const elTileCounts = document.querySelector('[data-tile-counts]');
     const elTileWidth = document.querySelector('[data-tile-width]');
     const elTileHeight = document.querySelector('[data-tile-height]');
     const elColumnCount = document.querySelector('[data-column-count]');
@@ -92,6 +130,8 @@
     const elOutputInformation = document.querySelector('[data-output-information]');
     const elOutputPreview = document.querySelector('[data-output-preview]');
     const elScale = document.querySelector('[data-indexed-preview-scale]');
+    const elRight = document.querySelector('[data-right]');
+    const elBottom = document.querySelector('[data-bottom]');
     const btnDownloadTileset = document.querySelector('[data-tileset-download]');
     const btnBackgroundWhite = document.querySelector('[data-page-bg-white]');
     const btnBackgroundTransparent = document.querySelector('[data-page-bg-transparent]');
@@ -99,130 +139,181 @@
     const btnBackgroundMagenta = document.querySelector('[data-page-bg-magenta]');
     const btnBackgroundBlue = document.querySelector('[data-page-bg-blue]');
     const btnBackgroundGreen = document.querySelector('[data-page-bg-green]');
-    const btnDownloadPalette = document.querySelector('[data-palette-download]');
-    const btnDownloadImage = document.querySelector('[data-indexed-download]');
+    const btnLoadTileset = document.querySelector('[data-load-tileset]');
 
+    // State
     let imageWidth = 0;
     let imageHeight = 0;
-    let image = null;
+    let pixels = null;
     let hoveredX = -1;
     let hoveredY = -1;
 
-    const updatePreview = () => {
-      if(!image) return;
+    const getValues = () => {
+      if(!pixels) return null;
+
+      let tileWidth, tileHeight, columnCount, rowCount, right, bottom;
+      if(elDefineBySize.checked) {
+        console.log('Defining by size');
+        tileWidth = parseInt(elTileWidth.value) || 0;
+        tileHeight = parseInt(elTileHeight.value) || 0;
+        columnCount = Math.floor(imageWidth / tileWidth);
+        rowCount = Math.floor(imageHeight / tileHeight);
+      } else {
+        console.log('Defining by count');
+        columnCount = parseInt(elColumnCount.value) || 0;
+        rowCount = parseInt(elRowCount.value) || 0;
+        tileWidth = Math.floor(imageWidth / columnCount);
+        tileHeight = Math.floor(imageHeight / rowCount);
+      }
+      
+      right = parseInt(elRight.value) || 0;
+      bottom = parseInt(elBottom.value) || 0;
 
       const scale = parseInt(elScale.value) || 1;
-      elOutputPreview.width = imageWidth * scale;
-      elOutputPreview.height = imageHeight * scale;
+      const scaledWidth = imageWidth * scale;
+      const scaledHeight = imageHeight * scale;
+      const scaledTileWidth = tileWidth * scale;
+      const scaledTileHeight = tileHeight * scale;
+      const scaledRight = right * scale;
+      const scaledBottom = bottom * scale;
+
+      const u0 = tileWidth  / imageWidth - (right / imageWidth);
+      const v0 = tileHeight / imageHeight - (bottom / imageHeight);
+
+      const hoveredTileX = isNaN(hoveredX) || hoveredX < 0 ? 0 : hoveredX;
+      const hoveredTileY = isNaN(hoveredY) || hoveredY < 0 ? 0 : hoveredY;
+      const hoveredU0 = hoveredTileX * tileWidth / imageWidth;
+      const hoveredV0 = hoveredTileY * tileHeight / imageHeight;
+      const hoveredU1 = hoveredU0 + u0;
+      const hoveredV1 = hoveredV0 + v0;
+      const hoveredTileIndex = hoveredTileY * columnCount + hoveredTileX;
+      
+      return {
+        tileWidth,
+        tileHeight,
+        columnCount,
+        rowCount,
+        right,
+        bottom,
+        scale,
+        scaledWidth,
+        scaledHeight,
+        scaledTileWidth,
+        scaledTileHeight,
+        scaledRight,
+        scaledBottom,
+        u0,
+        v0,
+        hoveredU0,
+        hoveredV0,
+        hoveredU1,
+        hoveredV1,
+        hoveredTileX,
+        hoveredTileY,
+        hoveredTileIndex,
+      }
+    }
+
+    const updatePreview = () => {
+      const v = getValues();
+      if(!v) return;
+      // console.log('Updating preview with values', v);
+
+      // Prepare canvas
+      elOutputPreview.width = v.scaledWidth;
+      elOutputPreview.height = v.scaledHeight;
       const ctx = elOutputPreview.getContext('2d');
       ctx.clearRect(0, 0, elOutputPreview.width, elOutputPreview.height);
       ctx.imageSmoothingEnabled = false;
-      ctx.drawImage(image, 0, 0, elOutputPreview.width, elOutputPreview.height);
 
-      // Draw grid lines
-      const tileWidth = parseInt(elTileWidth.value) || 0;
-      const tileHeight = parseInt(elTileHeight.value) || 0;
-      const scaledTileWidth = tileWidth * scale;
-      const scaledTileHeight = tileHeight * scale;
-      const columnCount = parseInt(elColumnCount.value) || 0;
-      const rowCount = parseInt(elRowCount.value) || 0;
+      // Resize pixels
+      const tempCanvas = document.createElement('canvas');
+      tempCanvas.width = imageWidth;
+      tempCanvas.height = imageHeight;
+      const tempCtx = tempCanvas.getContext('2d');
+      const imageData = tempCtx.createImageData(imageWidth, imageHeight);
+      imageData.data.set(pixels);
+      tempCtx.putImageData(imageData, 0, 0);
+      ctx.drawImage(tempCanvas, 0, 0, elOutputPreview.width, elOutputPreview.height);
+
+      // Draw blue overflow area for right and bottom cutoff
+      ctx.fillStyle = 'rgba(0,0,255,0.5)';
+      if(v.right > 0) {
+        ctx.fillRect(v.scaledWidth - v.scaledRight, 0, v.scaledRight, elOutputPreview.height);
+      }
+      if(v.bottom > 0) {
+        ctx.fillRect(0, v.scaledHeight - v.scaledBottom, elOutputPreview.width, v.scaledBottom);
+      }
+
+      // Draw red grid lines for tile boundaries
       ctx.strokeStyle = 'rgba(255,0,0,1)';
-      for(let x = scaledTileWidth; x < elOutputPreview.width; x += scaledTileWidth) {
+      for (let x = v.scaledTileWidth; x < elOutputPreview.width; x += v.scaledTileWidth) {
         ctx.beginPath();
         ctx.moveTo(x, 0);
         ctx.lineTo(x, elOutputPreview.height);
         ctx.stroke();
       }
-      for(let y = scaledTileHeight; y < elOutputPreview.height; y += scaledTileHeight) {
+      for (let y = v.scaledTileHeight; y < elOutputPreview.height; y += v.scaledTileHeight) {
         ctx.beginPath();
         ctx.moveTo(0, y);
         ctx.lineTo(elOutputPreview.width, y);
         ctx.stroke();
       }
 
-      const u0 = tileWidth / imageWidth;
-      const v0 = tileHeight / imageHeight;
-      const hoveredU0 = hoveredX != -1 && hoveredY != -1 ? (hoveredX * tileWidth / imageWidth) : 0; 
-      const hoveredV0 = hoveredX != -1 && hoveredY != -1 ? (hoveredY * tileHeight / imageHeight) : 0;
-      const hoveredU1 = hoveredU0 + u0;
-      const hoveredV1 = hoveredV0 + v0;
-
       elOutputInformation.value = [
-        hoveredX != -1 ? `Hovered Tile: ${hoveredX}, ${hoveredY} (${hoveredY * columnCount + hoveredX})` : 'Hovered Tile: None',
-        hoveredX != -1 ? `Hovered UV: ${(hoveredU0).toFixed(4)}, ${(hoveredV0).toFixed(4)} -> ${(hoveredU1).toFixed(4)}, ${(hoveredV1).toFixed(4)}` : 'Hovered UV: None',
+        v.hoveredX != -1 ? `Hovered Tile: ${v.hoveredTileX}, ${v.hoveredTileY} (${v.hoveredTileIndex})` : 'Hovered Tile: None',
+        v.hoveredX != -1 ? `Hovered UV: ${(v.hoveredU0).toFixed(4)}, ${(v.hoveredV0).toFixed(4)} -> ${(v.hoveredU1).toFixed(4)}, ${(v.hoveredV1).toFixed(4)}` : 'Hovered UV: None',
         `Image Width: ${imageWidth}`,
         `Image Height: ${imageHeight}`,
-        `Tile Width: ${elTileWidth.value}`,
-        `Tile Height: ${elTileHeight.value}`,
-        `Column Count: ${columnCount}`,
-        `uv: ${u0.toFixed(4)}, ${v0.toFixed(4)}`,
-        `Row Count: ${rowCount}`,
-        `Tile count: ${columnCount * rowCount}`,
+        `Tile Width: ${v.tileWidth}`,
+        `Tile Height: ${v.tileHeight}`,
+        `Column Count: ${v.columnCount}`,
+        `uv: ${v.u0.toFixed(4)}, ${v.v0.toFixed(4)}`,
+        `Row Count: ${v.rowCount}`,
+        `Tile count: ${v.columnCount * v.rowCount}`,
       ].join('\n');
     }
 
-    elTileWidth.addEventListener('input', () => {
-      if(imageWidth) {
-        const tileWidth = parseInt(elTileWidth.value);
-        const columnCount = Math.floor(imageWidth / tileWidth);
-        elColumnCount.value = columnCount;
-      }
+    elTileWidth.addEventListener('input', updatePreview);
+    elTileHeight.addEventListener('input', updatePreview);
+    elColumnCount.addEventListener('input', updatePreview);
+    elRowCount.addEventListener('input', updatePreview);
+    elRight.addEventListener('input', updatePreview);
+    elBottom.addEventListener('input', updatePreview);
+    elScale.addEventListener('input', updatePreview);
+    btnBackgroundWhite.addEventListener('click', () => document.body.style.background = 'white');
+    btnBackgroundTransparent.addEventListener('click', () => document.body.style.background = 'black');
+    btnBackgroundCheckerboard.addEventListener('click', () => document.body.style.background = 'repeating-conic-gradient(#ccc 0% 25%, #eee 0% 50%) 50% / 20px 20px');
+    btnBackgroundMagenta.addEventListener('click', () => document.body.style.background = 'magenta');
+    btnBackgroundBlue.addEventListener('click', () => document.body.style.background = 'blue');
+    btnBackgroundGreen.addEventListener('click', () => document.body.style.background = 'green');
+
+    elDefineBySize.addEventListener('change', () => {
+      if (elDefineBySize.checked) {
+        elTileSizes.style.display = '';
+        elTileCounts.style.display = 'none';
+      } 
       updatePreview();
     });
 
-    elTileHeight.addEventListener('input', () => {
-      if(imageHeight) {
-        const tileHeight = parseInt(elTileHeight.value);
-        const rowCount = Math.floor(imageHeight / tileHeight);
-        elRowCount.value = rowCount;
-      }
-      updatePreview();
-    });
-
-    elColumnCount.addEventListener('input', () => {
-      if(!imageWidth) {
-        alert('Set an image first to calculate tile width from column count');
-        return;
-      }
-
-      const columnCount = parseInt(elColumnCount.value);
-      const tileWidth = Math.floor(imageWidth / columnCount);
-      elTileWidth.value = tileWidth;
-      updatePreview();
-    });
-
-    elRowCount.addEventListener('input', () => {
-      if(!imageHeight) {
-        alert('Set an image first to calculate tile height from row count');
-        return;
-      }
-
-      const rowCount = parseInt(elRowCount.value);
-      const tileHeight = Math.floor(imageHeight / rowCount);
-      elTileHeight.value = tileHeight;
-      updatePreview();
-    });
-
-    elScale.addEventListener('input', () => {
+    elDefineByCount.addEventListener('change', () => {
+      if (elDefineByCount.checked) {
+        elTileSizes.style.display = 'none';
+        elTileCounts.style.display = '';
+      } 
       updatePreview();
     });
 
     elOutputPreview.addEventListener('mousemove', (e) => {
-      if(!image) return;
-
-      const scale = parseInt(elScale.value) || 1;
-      const tileWidth = parseInt(elTileWidth.value) || 0;
-      const tileHeight = parseInt(elTileHeight.value) || 0;
-      const columnCount = parseInt(elColumnCount.value) || 0;
-      const rowCount = parseInt(elRowCount.value) || 0;
+      const values = getValues();
+      if(!values) return;
 
       const rect = elOutputPreview.getBoundingClientRect();
-      const x = Math.floor((e.clientX - rect.left) / scale);
-      const y = Math.floor((e.clientY - rect.top) / scale);
-      hoveredX = Math.floor(x / tileWidth);
-      hoveredY = Math.floor(y / tileHeight);
-
-      if(hoveredX < 0 || hoveredX >= columnCount || hoveredY < 0 || hoveredY >= rowCount) {
+      const x = Math.floor((e.clientX - rect.left) / values.scale);
+      const y = Math.floor((e.clientY - rect.top) / values.scale);
+      hoveredX = Math.floor(x / values.tileWidth);
+      hoveredY = Math.floor(y / values.tileHeight);
+      if(hoveredX < 0 || hoveredX >= values.columnCount || hoveredY < 0 || hoveredY >= values.rowCount) {
         hoveredX = -1;
         hoveredY = -1;
       }
@@ -239,65 +330,144 @@
     // File
     elFileInput.addEventListener('change', (e) => {
       elOutputError.style.display = 'none';
+      pixels = null;
 
-      if(!elFileInput.files.length) {
+      if (!elFileInput.files.length) {
         elOutputError.textContent = 'No file selected';
         elOutputError.style.display = 'block';
         return;
       }
 
       const file = elFileInput.files[0];
-      image = new Image();
-      image.onload = () => {
-        imageWidth = image.width;
-        imageHeight = image.height;
-        const tileWidth = parseInt(elTileWidth.value);
-        const tileHeight = parseInt(elTileHeight.value);
-        const columnCount = Math.floor(imageWidth / tileWidth);
-        const rowCount = Math.floor(imageHeight / tileHeight);
-        elColumnCount.value = columnCount;
-        elRowCount.value = rowCount;
-        updatePreview();
-      };
-      image.onerror = () => {
-        image = null;
-        elOutputError.textContent = 'Failed to load image';
-        elOutputError.style.display = 'block';
-        updatePreview();
-      };
-      image.src = URL.createObjectURL(file);
+
+      if (file.name.endsWith('.dpt')) {
+        // Load DPT file
+        const reader = new FileReader();
+
+        reader.onload = () => {
+          const arrayBuffer = reader.result;
+          const data = new Uint8Array(arrayBuffer);
+          if (data[0] !== 'D'.charCodeAt(0) || data[1] !== 'P'.charCodeAt(0) || data[2] !== 'T'.charCodeAt(0)) {
+            elOutputError.textContent = 'Invalid DPT file';
+            elOutputError.style.display = 'block';
+            return;
+          } else if (data[3] !== 0x01) {
+            elOutputError.textContent = 'Unsupported DPT version';
+            elOutputError.style.display = 'block';
+            return;
+          }
+
+          // Begin color indexes
+          const width = (
+            data[4] |
+            (data[5] << 8) |
+            (data[6] << 16) |
+            (data[7] << 24)
+          )
+          const height = (
+            data[8] |
+            (data[9] << 8) |
+            (data[10] << 16) |
+            (data[11] << 24)
+          );
+
+          imageWidth = width;
+          imageHeight = height;
+
+          if(data.length < 12 + width * height) {
+            elOutputError.textContent = 'Invalid DPT file: not enough pixel data';
+            elOutputError.style.display = 'block';
+            return;
+          }
+
+          const uniqueIndexes = [];
+          for (let i = 0; i < width * height; i++) {
+            const colorIndex = data[12 + i];
+            if (!uniqueIndexes.includes(colorIndex)) {
+              uniqueIndexes.push(colorIndex);
+            }
+          }
+
+          const adhocPalette = [];
+          for (let i = 0; i < uniqueIndexes.length; i++) {
+            const index = uniqueIndexes[i];
+            // Get the most different possible color for this index
+            const color = [
+              (index * 37) % 256,
+              (index * 61) % 256,
+              (index * 97) % 256,
+              255
+            ];
+            adhocPalette[index] = color;
+          }
+
+          pixels = new Uint8Array(width * height * 4);
+          for (let i = 0; i < width * height; i++) {
+            const colorIndex = data[12 + i];
+            const color = adhocPalette[colorIndex];
+            pixels[i * 4] = color[0];
+            pixels[i * 4 + 1] = color[1];
+            pixels[i * 4 + 2] = color[2];
+            pixels[i * 4 + 3] = color[3];
+          }
+
+          updatePreview();
+        }
+
+        reader.onerror = () => {
+          elOutputError.textContent = 'Failed to read file';
+          elOutputError.style.display = 'block';
+        }
+
+        reader.readAsArrayBuffer(file);
+      } else {
+        const image = new Image();
+        image.onload = () => {
+          imageWidth = image.width;
+          imageHeight = image.height;
+
+          // Pixels
+          const tempCanvas = document.createElement('canvas');
+          tempCanvas.width = imageWidth;
+          tempCanvas.height = imageHeight;
+          const tempCtx = tempCanvas.getContext('2d');
+          tempCtx.drawImage(image, 0, 0);
+          const imageData = tempCtx.getImageData(0, 0, imageWidth, imageHeight);
+          pixels = imageData.data;
+
+          updatePreview();
+        };
+        image.onerror = () => {
+          pixels = null;
+          elOutputError.textContent = 'Failed to load image';
+          elOutputError.style.display = 'block';
+          updatePreview();
+        };
+        image.src = URL.createObjectURL(file);
+      }
     });
 
     btnDownloadTileset.addEventListener('click', () => {
-      if(!image) {
-        alert('No image loaded');
+      const v = getValues();
+      if(!v) {
+        alert('No valid tileset to download');
         return;
       }
 
-      const tileWidth = parseInt(elTileWidth.value);
-      const tileHeight = parseInt(elTileHeight.value);
-      const columnCount = parseInt(elColumnCount.value);
-      const rowCount = parseInt(elRowCount.value);
-      const u0 = tileWidth / imageWidth;
-      const v0 = tileHeight / imageHeight;
-      const tileCount = columnCount * rowCount;
-
+      // Header: DTF0, tileWidth, tileHeight, columnCount, rowCount, right, bottom, u0, v0
       const headerBytes = new Uint8Array([
-        'D'.charCodeAt(0),// Dusk
-        'T'.charCodeAt(0),// Tileset
-        'F'.charCodeAt(0),// File/Format
+        'D'.charCodeAt(0), // Dusk
+        'T'.charCodeAt(0), // Tileset
+        'F'.charCodeAt(0), // File/Format
         0x00, // version
-        tileWidth & 0xFF,// Tile width (uint16_t)
-        (tileWidth >> 8) & 0xFF,
-        tileHeight & 0xFF,// Tile height (uint16_t)
-        (tileHeight >> 8) & 0xFF,
-        columnCount & 0xFF,// Column count (uint16_t)
-        (columnCount >> 8) & 0xFF,
-        rowCount & 0xFF,// Row count (uint16_t)
-        (rowCount >> 8) & 0xFF,
-        // Float32_t UV step (u0, v0)
-        ...new Uint8Array(new Float32Array([u0]).buffer),
-        ...new Uint8Array(new Float32Array([v0]).buffer),
+        v.tileWidth & 0xFF, (v.tileWidth >> 8) & 0xFF,
+        v.tileHeight & 0xFF, (v.tileHeight >> 8) & 0xFF,
+        v.columnCount & 0xFF, (v.columnCount >> 8) & 0xFF,
+        v.rowCount & 0xFF, (v.rowCount >> 8) & 0xFF,
+        v.right & 0xFF, (v.right >> 8) & 0xFF,
+        v.bottom & 0xFF, (v.bottom >> 8) & 0xFF,
+        ...new Uint8Array(new Float32Array([v.u0]).buffer),
+        ...new Uint8Array(new Float32Array([v.v0]).buffer),
       ]);
 
       // Download file
@@ -307,25 +477,65 @@
       a.href = url;
       a.download = 'tileset.dtf';
       a.click();
+      URL.revokeObjectURL(url);
     });
 
-    btnBackgroundWhite.addEventListener('click', () => {
-      document.body.style.background = 'white';
-    });
-    btnBackgroundTransparent.addEventListener('click', () => {
-      document.body.style.background = 'black';
-    });
-    btnBackgroundCheckerboard.addEventListener('click', () => {
-      document.body.style.background = 'repeating-conic-gradient(#ccc 0% 25%, #eee 0% 50%) 50% / 20px 20px';
-    });
-    btnBackgroundMagenta.addEventListener('click', () => {
-      document.body.style.background = 'magenta';
-    });
-    btnBackgroundBlue.addEventListener('click', () => {
-      document.body.style.background = 'blue';
-    });
-    btnBackgroundGreen.addEventListener('click', () => {
-      document.body.style.background = 'green';
+    btnLoadTileset.addEventListener('click', () => {
+      // Browse for file.
+      const input = document.createElement('input');
+      input.type = 'file';
+      input.accept = '.dtf';
+      input.addEventListener('change', (e) => {
+        const files = e?.target?.files;
+        if (!files || !files.length || !files[0]) {
+          alert('No file selected');
+          return;
+        }
+
+        const file = files[0];
+        if (!file.name.endsWith('.dtf')) {
+          alert('Invalid file type. Please select a .dtf file.');
+          return;
+        }
+
+        const reader = new FileReader();
+        reader.onload = () => {
+          const arrayBuffer = reader.result;
+          const data = new Uint8Array(arrayBuffer);
+          if (data[0] !== 'D'.charCodeAt(0) || data[1] !== 'T'.charCodeAt(0) || data[2] !== 'F'.charCodeAt(0)) {
+            alert('Invalid DTF file');
+            return;
+          }
+
+          if (data[3] !== 0x00) {
+            alert('Unsupported DTF version');
+            return;
+          }
+
+          const tileWidth = data[4] | (data[5] << 8);
+          const tileHeight = data[6] | (data[7] << 8);
+          const columnCount = data[8] | (data[9] << 8);
+          const rowCount = data[10] | (data[11] << 8);
+          const right = data[12] | (data[13] << 8);
+          const bottom = data[14] | (data[15] << 8);
+
+          // Switch to using size definition
+          elDefineBySize.checked = true;
+          elTileWidth.value = tileWidth;
+          elTileHeight.value = tileHeight;
+          elTileSizes.style.display = '';
+          elTileCounts.style.display = 'none';
+          elRight.value = right;
+          elBottom.value = bottom;
+
+          updatePreview();
+        };
+        reader.onerror = () => {
+          alert('Failed to read file');
+        };
+        reader.readAsArrayBuffer(file);
+      });
+      input.click();
     });
 
     // Init