var LN2 = Math.log(2); function determinant(rows, rank, rowStart, rowMask, colMask, detCache) { var cacheKey = rowMask + '-' + colMask; var fullRank = rows.length; if (detCache.hasOwnProperty(cacheKey)) { return detCache[cacheKey]; } if (rank === 1) { var colStart = Math.round(Math.log(((1 << fullRank) - 1) & ~colMask) / LN2); return rows[rowStart][colStart]; } var subRowMask = rowMask | (1 << rowStart); var subRowStart = rowStart + 1; while (rowMask & (1 << subRowStart)) { subRowStart++; } var sum = 0; for (var j = 0, colLocalIdx = 0; j < fullRank; j++) { var colTag = 1 << j; if (!(colTag & colMask)) { sum += (colLocalIdx % 2 ? -1 : 1) * rows[rowStart][j] * determinant(rows, rank - 1, subRowStart, subRowMask, colMask | colTag, detCache); colLocalIdx++; } } detCache[cacheKey] = sum; return sum; } export function buildTransformer(src, dest) { var mA = [ [src[0], src[1], 1, 0, 0, 0, -dest[0] * src[0], -dest[0] * src[1]], [0, 0, 0, src[0], src[1], 1, -dest[1] * src[0], -dest[1] * src[1]], [src[2], src[3], 1, 0, 0, 0, -dest[2] * src[2], -dest[2] * src[3]], [0, 0, 0, src[2], src[3], 1, -dest[3] * src[2], -dest[3] * src[3]], [src[4], src[5], 1, 0, 0, 0, -dest[4] * src[4], -dest[4] * src[5]], [0, 0, 0, src[4], src[5], 1, -dest[5] * src[4], -dest[5] * src[5]], [src[6], src[7], 1, 0, 0, 0, -dest[6] * src[6], -dest[6] * src[7]], [0, 0, 0, src[6], src[7], 1, -dest[7] * src[6], -dest[7] * src[7]] ]; var detCache = {}; var det = determinant(mA, 8, 0, 0, 0, detCache); if (det === 0) { return; } var vh = []; for (var i = 0; i < 8; i++) { for (var j = 0; j < 8; j++) { vh[j] == null && (vh[j] = 0); vh[j] += ((i + j) % 2 ? -1 : 1) * determinant(mA, 7, i === 0 ? 1 : 0, 1 << i, 1 << j, detCache) / det * dest[i]; } } return function (out, srcPointX, srcPointY) { var pk = srcPointX * vh[6] + srcPointY * vh[7] + 1; out[0] = (srcPointX * vh[0] + srcPointY * vh[1] + vh[2]) / pk; out[1] = (srcPointX * vh[3] + srcPointY * vh[4] + vh[5]) / pk; }; }