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node_modules/pngjs/lib/interlace.js

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+"use strict";
+
+// Adam 7
+//   0 1 2 3 4 5 6 7
+// 0 x 6 4 6 x 6 4 6
+// 1 7 7 7 7 7 7 7 7
+// 2 5 6 5 6 5 6 5 6
+// 3 7 7 7 7 7 7 7 7
+// 4 3 6 4 6 3 6 4 6
+// 5 7 7 7 7 7 7 7 7
+// 6 5 6 5 6 5 6 5 6
+// 7 7 7 7 7 7 7 7 7
+
+let imagePasses = [
+  {
+    // pass 1 - 1px
+    x: [0],
+    y: [0],
+  },
+  {
+    // pass 2 - 1px
+    x: [4],
+    y: [0],
+  },
+  {
+    // pass 3 - 2px
+    x: [0, 4],
+    y: [4],
+  },
+  {
+    // pass 4 - 4px
+    x: [2, 6],
+    y: [0, 4],
+  },
+  {
+    // pass 5 - 8px
+    x: [0, 2, 4, 6],
+    y: [2, 6],
+  },
+  {
+    // pass 6 - 16px
+    x: [1, 3, 5, 7],
+    y: [0, 2, 4, 6],
+  },
+  {
+    // pass 7 - 32px
+    x: [0, 1, 2, 3, 4, 5, 6, 7],
+    y: [1, 3, 5, 7],
+  },
+];
+
+exports.getImagePasses = function (width, height) {
+  let images = [];
+  let xLeftOver = width % 8;
+  let yLeftOver = height % 8;
+  let xRepeats = (width - xLeftOver) / 8;
+  let yRepeats = (height - yLeftOver) / 8;
+  for (let i = 0; i < imagePasses.length; i++) {
+    let pass = imagePasses[i];
+    let passWidth = xRepeats * pass.x.length;
+    let passHeight = yRepeats * pass.y.length;
+    for (let j = 0; j < pass.x.length; j++) {
+      if (pass.x[j] < xLeftOver) {
+        passWidth++;
+      } else {
+        break;
+      }
+    }
+    for (let j = 0; j < pass.y.length; j++) {
+      if (pass.y[j] < yLeftOver) {
+        passHeight++;
+      } else {
+        break;
+      }
+    }
+    if (passWidth > 0 && passHeight > 0) {
+      images.push({ width: passWidth, height: passHeight, index: i });
+    }
+  }
+  return images;
+};
+
+exports.getInterlaceIterator = function (width) {
+  return function (x, y, pass) {
+    let outerXLeftOver = x % imagePasses[pass].x.length;
+    let outerX =
+      ((x - outerXLeftOver) / imagePasses[pass].x.length) * 8 +
+      imagePasses[pass].x[outerXLeftOver];
+    let outerYLeftOver = y % imagePasses[pass].y.length;
+    let outerY =
+      ((y - outerYLeftOver) / imagePasses[pass].y.length) * 8 +
+      imagePasses[pass].y[outerYLeftOver];
+    return outerX * 4 + outerY * width * 4;
+  };
+};