ImageResizer AspectRatioPlugin

AspectRatioPlugin.cs

    /// <summary>
    /// A ImageResizerPlugin that uses a special ascpetratio command to calculate the height.
    /// </summary>
    /// <author>Per Osbäck</author>
    public class AspectRatioPlugin : IPlugin
    {
        public AspectRatioPlugin()
        {
        }

        #region IPlugin Members

        public IPlugin Install(ImageResizer.Configuration.Config c)
        {
            c.Plugins.add_plugin(this);
            c.Pipeline.Rewrite += new UrlRewritingEventHandler(Pipeline_RewriteDefaults);
            return this;
        }

        void Pipeline_RewriteDefaults(IHttpModule sender, HttpContext context, IUrlEventArgs e)
        {
            var aspectW = e.QueryString["aspectw"];
            var aspectH = e.QueryString["aspecth"];
            if (aspectH == null && aspectW == null)
            {
                return;
            }

            double aspectratio = 0;
            if (double.TryParse(aspectW ?? aspectH, out aspectratio) && aspectratio > 0)
            {
                int parameterValue = 0;
                if (aspectW != null && int.TryParse(e.QueryString["width"], out parameterValue))
                {
                    UpdateParameters("height", (int)(parameterValue / aspectratio), e);
                }
                else if (aspectH != null && int.TryParse(e.QueryString["height"], out parameterValue))
                {
                    UpdateParameters("width", (int)(parameterValue * aspectratio), e);
                }
            }
        }

        private void UpdateParameters(string targetKey, int targetValue, IUrlEventArgs e)
        {
            e.QueryString.Remove(targetKey);
            e.QueryString.Add(targetKey, targetValue.ToString());
        }

        public bool Uninstall(ImageResizer.Configuration.Config c)
        {
            c.Plugins.remove_plugin(this);
            c.Pipeline.RewriteDefaults -= new UrlRewritingEventHandler(Pipeline_RewriteDefaults);
            return true;
        }

        #endregion
    }

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