what's the difference in visualizing and envisioning ?

Visualizing. Is take information in text form, and putting into a pictorial form.

Envisioning. Means putting into concrete form some plan for the future. Imagine as a future possibility.

Envisaging often relates to planning real-world projects. When you envision something, it's usually more hypothetical, imaginary, or removed from reality. The difference is subtle, but think of it this way: Envisaging usually involves something real, while envisioning involves mostly imaginary elements

The only difference is the context of  creation vs memory.

A psychological picture shaped by the activity of the creative mind as a staff; something envisioned. "conception|notion|imagining". Representation (thing).

Shenidan key bovad manandeh didan!It means:A picture is worth a thousand words.

First there is a great discrepancy between using the verbs "envision/envisioning" and the verb "envisage/envisaging."

ENVISION/envisioning simply means to be picturing something in one's MIND (not literally seeing the object of thought) - something that ALREADY EXISTS: a memory of a painting, or sunset; the image of a rose, or a cat . . . .

ENVISAGE relates to something completely new - to conceive and image or picture of something that has never been created prior, most especially relating to a future POSSIBILITY - it is used in the scientific community most precisely, likely due to "blind reviews" of papers submitted to peer-reviewed journals to meet publication requirements of internationally read journals. (And people enjoying their criticisms to be read "nameless" by the person who wants their paper published, which can mean submitting to the "blind reviewer's" corrections).

Be cautious-

The adjective "VISUAL" is actually seeing the "subject" with one's eye - literally, no exceptions; or is something that one can see and later make "visual" in one's mind.

The VERB "VISUALIZING" is "non-exact." It is an ambiguous verb to use and I suggest avoiding the use of it, most especially if you are distinguishing an "idea" or a "concept" from something that already exists.  It simply means to form a mental image or vision and thus encompasses both "envisioning" and "envisaging" so avoid it!  If not, use "visualizing" in your sentence with exceptional specificity. It is used clearly in quality writing; I just urge you to prefer the best word usage that is available to you.  Possibly, you may fall into unnecessary less disciplined (ambiguous) writing as well as opening the door to being nitpicked or attacked by "prideful/snobbish/pseudo-intellectuals/unkind" people, which is always unpleasant.

Best of success with your writing!

I suggest that you buy an unabridged American Heritage Dictionary - NOT the paperback, the size difference isn't worth it.

"Visualizing" means creating an actual visual image in your mind.  "Envisioning" means planning, thinking about the future. You can visualize things from the past. You envision the future. 

Sometimes, visualizing is part of envisioning. "If you open your own business, visualize yourself sitting behind your desk, in your own office, with the letters CEO on the door." 

Envisaging often relates to planning real-world projects. When you envision something, it's usually more hypothetical, imaginary, or removed from reality. The difference is subtle, but think of it this way: Envisaging usually involves something real, while envisioning involves mostly imaginary elements

one is BIGGER than the other one.

Whoever keep thumbing me down better realise they asking for trouble.