What is the minimum number of straight lines required to make the given image?

Let's count the straight lines category by category to avoid duplication:
1. Horizontal Lines: * Bottom-most base line = $1$
* Middle horizontal line forming the base of the inner inverted triangle/rectangles = $1$
* Total Horizontal lines = $2$

2. Vertical Lines:
* One main central vertical line running from the top apex to the bottom base = $1$
* Total Vertical lines = $1$

3. Slanting / Diagonal Lines:
* Main outer boundary slanting lines: $2$ (top left, top right) + $2$ (middle left, middle right) = $4$
* Inner triangles and intersecting slanting lines:
* Upper triangle structure slanting lines = $4$
* Lower interior intersecting slanting lines forming the stars/diamonds = $4$

* Total Slanting lines = $4+4+4=12$

Total minimum number of straight lines = $2\text{ (Horizontal)}+1\text{ (Vertical)}+12\text{ (Slanting)}=15$.