You could do that importing an image of the sloper and tracing over that. You would would have to draw a square on the sloper first so that you can use that as a reference for scaling of the image to the correct size when loading it.
That being said… in all honesty drafting a basic bodice block to your measurements is such a simple pattern to draft it may actually be quicker than dealing with an image and tracing.
Once you have the basic block you can then use that as a template to create different styles. Also there is no need to trace over a basic block… you just add new points and curves that will define the outline of pattern piece you wish to create from a block.
I think maybe some explantion of draftblocks, slopers will help.
A sloper is a basic pattern piece that is derived from either drafting or draping on a dress form. They are generally not meant to be used as is, but rather manipluated to create styled pattern pieces. The sloper represents the “grade points” of the body. Think of a sloper as one of the canvas cover pieces that are on a dress form.
In drafting patterns most systems start with drafting the same basic block that again establishes certain points based on the measurments. From there you then draft what ever style.
In Seamly there are 2 modes Draft and Piece… where in draft mode we to"draft block" which may be just the basic block (analagous to a sloper) or also include the style points. While a draft block can display lines, it’s really about locating points and curves… which are then connected to create an outline and saved as a “pattern piece”. You then detail the pattern pieces in piece mode. You can create any number of pieces from a single draft block. Parts you want to hide can be placed in a group and hidden.
Here’s another method that may be of help… If you are able to draw out your full sized sloper on a piece of paper, and locate each corner point on a grid from a reference point, and if you know what sizes that the sloper is created from - you can enter it as a draft block. I outlined such a method when I drafted a shift dress an employee of mine draped on a dress form.