The Image options allow a small amount of image manipulation and will only be available when you have an image in the backcloth of a model.
Image files, such as bitmaps and JPEGs, do not normally contain a co-ordinate system. It is often necessary to match an image to a co-ordinate system. The Image Transform option allows you to do this. Firstly, you need to have loaded the image in question into a backcloth for a model. During this process, you must define the image properties using a dialog box.
The X and Y defines the co-ordinates of the top left of the image. The Width and Height fields define the size of the image. The default values that are displayed are at 0,0 and the size of the image in pixels. If you know these values, you can enter them here rather use the transformation option.
If you do not know the co-ordinates for the image, you need to use the transformation option. You will firstly be asked to indicate two known points in the image. If the image is a scan of a plan, then you may have grid lines or stations of known co-ordinates. You will then be asked to enter the correct co-ordinates for these points using a two-point transformation dialog box.
After you have entered these values and selected OK, the image co-ordinate system will be calculated. This image can then be used as a backcloth models or to digitise information, such as contours, from the image.
Note that only orthogonal images can be handled where there is no rotation of the co-ordinate system. You should also be aware that the accuracy of any digitised data is only as accurate as the initial image scale.
The Image Border option allows you to show the border of an image in the dedicated CAD backcloth. You will be asked to define the layer, line style, pen and text style for the border. A rectangle will be created together with a text item to the bottom left corner of the rectangle which show the name of the image, not its full path.