Scaling Raster Images

You can control the size of a raster image in a drawing to match the scale of the drawing.

You can specify the raster image scale factor when you attach the image so that the scale of the geometry in the image matches the scale of the geometry in the drawing. The default image scale factor is 1, and the default unit for all images is “Unitless.” The image file can contain resolution information defining the dots per inch (DPI), relating to how the image was scanned.

If an image has resolution information, the program combines this information with the scale factor and the unit of measurement of the drawing to scale the image in your drawing. For example, if your raster image is a scanned blueprint on which the scale is 1 inch equals 50 feet, or 1:600, and your drawing is set up so that 1 unit represents 1 inch, then in the Image dialog box under Scale, select Specify On-Screen. To scale the image, you clear Specify On-Screen, and then enter 600 in Scale. The image is then attached at a scale that brings the geometry in the image into alignment with the geometry in the drawing.

If no resolution information is defined with the attached image file, the width of the raster image is set to one unit. Thus, when the image file is attached, the image width in units is equal to the raster image scale factor.