copy cropped image to center of another black image

i need to copy a cropped image to the center of another black one but i have this error "Subscripted assignment dimension mismatch." i can't find where is the error my code is:

blackimg=uint8(zeros(32,32));

blackimg=im2bw(blackimg);
% // Get the centre of the picture frame
[rowsblack, colsblack] = size(blackimg);
picblackCenRow = round(rowsblack / 2);
picblackCenCol = round(colsblack / 2);

% // Get dimensions of parrot image
[rowscrop, colscrop] = size(crop);
% Determine the pasting boundaries.
r1 = picblackCenRow-round(rowscrop/2);
c1 = picblackCenCol-round(colscrop/2);
r2 = picblackCenRow+round(rowscrop/2)-1;
r2 = min([r2, rowsblack]);
c2 = picblackCenCol+round(colscrop/2)-1;
c2 = min([c2, colsblack]);
% // Place the parrot in the centre
blackimg(r1 : r2, c1:c2) = crop;

my crop image size is 28*7 where is the error please thanks in advance