Flora on Sand by Paul Klee

Normal Sudoku rules apply. Numbers outside the grid are the sum of the numbers on the indicated diagonal. Numbers can repeat on diagonals, if other rules allow. Numbers in cages sum to the number in the top left corner of the cage. There are three magic squares (3x3 areas where the sum of all rows, columns and major diagonals sum to 15). The centers of two of the magic squares are in two of the 1x1 colored cells in Paul Klee's painting. The third center is to be determined by the solver.