APL (Dyalog Extended), 48 bytes (SBCS)

{(=/⍵-⍥⍴e)∧i≡,e←(⊂∘⊃+∘⍳∘|1+⊃∘⌽-⊃)i←⍸⍵}0⍉⍤⌂deb⍣2⊢

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APL (Dyalog Extended), 48 bytes (SBCS)

Anonymous tacit prefix function. Takes Boolean (0/1) matrix with 0s indicating the shape. Requires 0-based indexing.

{(=/⍵-⍥⍴e)∧i≡,e←(⊂∘⊃+∘⍳∘|1+⊃∘⌽-⊃)i←⍸⍵}1⍉⍤⌂deb⍣2⊢

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0...⊢⁠ with 0 as left argument and the unmodified argument as right argument:

...⍣2 repeat twice

...⍤⌂debdelete ending (leading and trailing) blanks (1s), then:

⍉ transpose (so we end up deleting the top and bottom blank rows too)

{...} apply the following lambda, with ⍵ representing its argument:

⍸⍵indices where there are 1s

i← save as i

(...) apply the following tacit function to that:

⊃ the [index of the] first [blank]

...- subtract that from:

⊃∘ the [index of the] first of the:

⌽ reversed [indices of blanks, i.e. the index of the last blank]

1+ increment that [to get inclusive range]

∘| take the absolute value of that [getting the absolute range], then:

∘⍳ get the indices of that range, then:

...+ add that to:

⊂∘ the whole of...

⊃ [index of the] first [blank, giving a matrix of indices of the entire supposed blank area]

e← save as e

, ravel into a list of indices

i≡ identical to the actual list of indices of blanks?

(...)∧ and...

⍵...e considering the argument and the matrix of supposed blanks...

-⍥ are the differences in...

⍴ shapes [between heights and widths]

=/ equal? [i.e. does the height-difference match the width-difference?]