Navigate while viewing extra large images in .NET

Blog category: Imaging

May 13, 2020

This article describes how to use the ImageMapTool class from VintaSoft Imaging .NET SDK for viewing large and extra large images.

Let's use JPEG2000 image with image size of 4067 megapixel (35878х113378 pixels) as an example.
Here is the screenshot of JPEG2000 image with 1% zoom in VintaSoft Imaging Demo:
Very large JPEG2000 image with 1% zoom in VintaSoft Imaging Demo

Here is the screenshot of JPEG2000 image with 10% zoom in VintaSoft Imaging Demo:
Very large JPEG2000 image with 10% zoom in VintaSoft Imaging Demo

While viewing a very large image it is often difficult to understand above what part of image you are at the moment and where to move to get to the desired location. Generally this inconvenience can be solved by scaling down the image and then scaling up the desired area. But in case when the decoding of image is rather resource-intensive it can take an unacceptable amount of time. Usage of image map using ImageMapTool class is comfortable and elegant way for solving the problem.

In VintaSoft Imaging Demo the image map can be enabled using menu item "View -> Image Map Settings...". The screenshot below shows the image map settings in VintaSoft Imaging Demo:
Default image map settings in VintaSoft Imaging Demo


In fact the image map is a small image viewer, which is located above the main image viewer and it shows the same image, but in other scaling mode. The screenshot below shows the image map settings with 1/25 scale factor relative to the current zoom factor of main image viewer:
Image map settings with custom scale factor in VintaSoft Imaging Demo


ImageMapTool class:

The ImageViewer.ViewerBufferSize property allows to specify the size, in megapixels, of rectangle of fully cached area around the visible area (yellow rectangle) in image viewer. The screenshot below shows the image viewer settings with 6 megapixels size of cached area around visible area in image viewer:
Image viewer settings with custom size of cached area around visible area in image viewer



Besides that, for very very large images is possible to use several ImageMapTool elements on image viewer at once, each with different relative scaling. This is possible owing to the CompositeVisualTool class, which allows to combine the functionality of several visual tools.
Here is C# code that shows how to create 2 image maps on image viewer:
// create the first image map tool
Vintasoft.Imaging.UI.VisualTools.ImageMapTool imageMap1 = new Vintasoft.Imaging.UI.VisualTools.ImageMapTool();
// specify that image map must be enabled
imageMap1.Enabled = true;
// specify that image map tool must show image in best fit mode
imageMap1.Zoom = 0;
// specify that image map must have size 200x200 pixels
imageMap1.Size = new System.Drawing.Size(200, 200);
// specify that image map must be shown at the left-top corner of image viewer
imageMap1.Anchor = Vintasoft.Imaging.UI.AnchorType.Left | Vintasoft.Imaging.UI.AnchorType.Top;
// specify that image map tool border must have red color
imageMap1.CanvasPen = new System.Drawing.Pen(System.Drawing.Color.Red);
// specify that the border of image's visible region in image map must have lime color
imageMap1.VisibleRectPen = new System.Drawing.Pen(System.Drawing.Color.Lime);

// create the second image map tool
Vintasoft.Imaging.UI.VisualTools.ImageMapTool imageMap2 = new Vintasoft.Imaging.UI.VisualTools.ImageMapTool();
// specify that image map must be enabled
imageMap2.Enabled = true;
// specify that image map tool must show image in 1/25 scale from image viewer zoom
imageMap2.Zoom = 1 / 25f;
// specify that image map must have size 200x200 pixels
imageMap1.Size = new System.Drawing.Size(200, 200);
// specify that image map must be shown at the left-bottom corner of image viewer
imageMap2.Anchor = Vintasoft.Imaging.UI.AnchorType.Left | Vintasoft.Imaging.UI.AnchorType.Bottom;
// specify that image map tool border must have red color
imageMap2.CanvasPen = new System.Drawing.Pen(System.Drawing.Color.Red);
// specify that the border of image's visible region in image map must have lime color
imageMap2.VisibleRectPen = new System.Drawing.Pen(System.Drawing.Color.Lime);

// create composite visual tool that combines first and second image map tools
Vintasoft.Imaging.UI.VisualTools.CompositeVisualTool compositeVisualTool = new Vintasoft.Imaging.UI.VisualTools.CompositeVisualTool(imageMap1, imageMap2);

// set composite visual tool as current visual tool of image viewer
imageViewer1.VisualTool = compositeVisualTool;

The screenshot below shows the image viewer with 2 image maps:
Image viewer with 2 image maps in VintaSoft Imaging Demo


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