It requires time and know-how to refine the scanned image into a workable chart with the appropriate number of colors. Some of the companies will supply you with the color image scanned onto a grid which you must then decipher as to color numbers, shading, etc. Others will tweak the image into a recognizable reproduction with symbols and color coding. Decide what sort of chart you wish to work from and make inquiries as to what type of output to expect. With the advances in computer imaging it is now possible to produce digital needlepoint canvases.
New technology allows for close calibration and high quality, quick drying inks.
A design can now be printed by computer directly on needlepoint canvas and the end result looks very much like a hand painted canvas. Close registration and detailed shading are now possible, and accuracy and speed are definite advantages over laborious copy-painting by hand. Geometric motifs are an example of designs which usually require stitch-painting. Some canvases now combine the best of both approaches by having less complex areas painted by computer and selected areas stitch-painted by hand. Computers will not magically design embroidery but they can be used very effectively to assist needleworkers in designing and charting.