fix LUMINANCE_ALPHA

src/ol/style/expressions.js

@@ -503,7 +503,7 @@ Operators['band'] = {
       for (let i = 0; i < bandCount; i++) {
         const colorIndex = Math.floor(i / 4);
         let bandIndex = i % 4;
-        if (bandIndex === bandCount - 1 && bandIndex === 1) {
+        if (i === bandCount - 1 && bandIndex === 1) {
           // LUMINANCE_ALPHA - band 1 assigned to rgb and band 2 assigned to alpha
           bandIndex = 3;
         }

test/rendering/cases/webgl-data-tile-6-band/main.js

@@ -0,0 +1,59 @@
+import DataTile from '../../../../src/ol/source/DataTile.js';
+import Map from '../../../../src/ol/Map.js';
+import TileLayer from '../../../../src/ol/layer/WebGLTile.js';
+import View from '../../../../src/ol/View.js';
+
+const size = [81, 99];
+
+const canvas = document.createElement('canvas');
+canvas.width = size[0];
+canvas.height = size[1];
+
+const context = canvas.getContext('2d');
+context.strokeStyle = 'white';
+context.textAlign = 'center';
+const lineHeight = 16;
+context.font = `${lineHeight}px sans-serif`;
+
+new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      source: new DataTile({
+        tileSize: size,
+        bandCount: 6,
+        loader: function (z, x, y) {
+          const halfWidth = size[0] / 2;
+          const halfHeight = size[1] / 2;
+          context.fillStyle = '#00AAFF';
+          context.fillRect(0, 0, size[0], size[1]);
+          context.fillStyle = 'white';
+          context.fillText(`z: ${z}`, halfWidth, halfHeight - lineHeight);
+          context.fillText(`x: ${x}`, halfWidth, halfHeight);
+          context.fillText(`y: ${y}`, halfWidth, halfHeight + lineHeight);
+          context.strokeRect(0, 0, size[0], size[1]);
+          const input = context.getImageData(0, 0, size[0], size[1]).data;
+          const length = input.length;
+          const output = new Uint8Array(length * 1.5);
+          for (let i = 0, j = 1; i < length; i += 4) {
+            output[j] = input[i];
+            output[j + 1] = input[i + 1];
+            output[j + 2] = input[i + 2];
+            output[j + 4] = input[i + 3];
+            j += 6;
+          }
+          return output;
+        },
+      }),
+      style: {
+        color: ['array', ['band', 2], ['band', 3], ['band', 4], ['band', 6]],
+      },
+    }),
+  ],
+  view: new View({
+    center: [0, 0],
+    zoom: 4,
+  }),
+});
+
+render({tolerance: 0.03});