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gaia/apps/camera/js/lib/camera-utils.js

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+define(function(require) {
+  /*jshint maxlen:false*/
+  'use strict';
+
+  var CameraUtils = {};
+
+  CameraUtils.scaleSizeToFitViewport = function(viewportSize, imageSize) {
+    var sw = viewportSize.width / imageSize.width,
+        sh = viewportSize.height / imageSize.height,
+        scale;
+
+    // Select the smaller scale to fit image completely within the viewport
+    scale = Math.min(sw, sh);
+
+    return {
+      width: imageSize.width * scale,
+      height: imageSize.height * scale
+    };
+  };
+
+  CameraUtils.scaleSizeToFillViewport = function(viewportSize, imageSize) {
+    var sw = viewportSize.width / imageSize.width,
+        sh = viewportSize.height / imageSize.height,
+        scale;
+
+    // Select the larger scale to fill and overflow viewport with image
+    scale = Math.max(sw, sh);
+
+    return {
+      width: imageSize.width * scale,
+      height: imageSize.height * scale
+    };
+  };
+
+  /**
+   * Get the maximum preview size (in terms of area) from a list of
+   * possible preview sizes.
+   *
+   * NOTE: If an `aspectRatio` value is provided, the search will be
+   * constrained to only accept preview sizes matching that aspect
+   * ratio.
+   *
+   * @param  {Array} previewSizes
+   * @param  {Number} aspectRatio
+   * @return {Object}
+   */
+  CameraUtils.getMaximumPreviewSize = function(previewSizes, aspectRatio) {
+
+    // Use a very small tolerance because we want an exact match if we are
+    // constraining to only include specific aspect ratios.
+    const ASPECT_TOLERANCE = 0.001;
+
+    var maximumArea = 0;
+    var maximumPreviewSize = null;
+    previewSizes.forEach(function(previewSize) {
+      var area = previewSize.width * previewSize.height;
+
+      if (aspectRatio) {
+        var ratio = previewSize.width / previewSize.height;
+        if (Math.abs(ratio - aspectRatio) > ASPECT_TOLERANCE) {
+          return;
+        }
+      }
+
+      if (area > maximumArea) {
+        maximumArea = area;
+        maximumPreviewSize = previewSize;
+      }
+    });
+
+    return maximumPreviewSize;
+  };
+
+  return CameraUtils;
+});