An time-delay-integration image sensor comprises a matrix of photosensitive pixels organized in rows and columns, a first matrix of memory cells associated with control and adding means to store accumulated brightness levels of several rows of pixels in a row of memory cells. The first memory cell matrix is provided with the control and adding means to store in its rows accumulated brightness levels of the rows of a first half of the pixel matrix. The sensor comprises a second memory cell matrix associated with the control and adding means to store accumulated brightness levels of the rows of the second half of the pixel matrix in a row of the second memory cell matrix. Means are provided for adding the levels accumulated in a row of the first memory cell matrix to the levels accumulated in a corresponding row of the second memory cell matrix.