1 files changed, 103 insertions, 0 deletions
diff --git a/src/projections/cea.cpp b/src/projections/cea.cpp
new file mode 100644
index 00000000..f8275b62
--- /dev/null
+++ b/src/projections/cea.cpp
@@ -0,0 +1,103 @@
+#define PJ_LIB__
+
+#include <errno.h>
+#include <math.h>
+
+#include "proj.h"
+#include "projects.h"
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double qp;
+    double *apa;
+};
+} // anonymous namespace
+
+PROJ_HEAD(cea, "Equal Area Cylindrical") "\n\tCyl, Sph&Ell\n\tlat_ts=";
+# define EPS    1e-10
+
+
+static XY e_forward (LP lp, PJ *P) {          /* Ellipsoidal, forward */
+    XY xy = {0.0,0.0};
+    xy.x = P->k0 * lp.lam;
+    xy.y = 0.5 * pj_qsfn (sin (lp.phi), P->e, P->one_es) / P->k0;
+    return xy;
+}
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    xy.x = P->k0 * lp.lam;
+    xy.y = sin(lp.phi) / P->k0;
+    return xy;
+}
+
+
+static LP e_inverse (XY xy, PJ *P) {          /* Ellipsoidal, inverse */
+    LP lp = {0.0,0.0};
+    lp.phi = pj_authlat(asin( 2. * xy.y * P->k0 / static_cast<struct pj_opaque*>(P->opaque)->qp), static_cast<struct pj_opaque*>(P->opaque)->apa);
+    lp.lam = xy.x / P->k0;
+    return lp;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    double t;
+
+    if ((t = fabs(xy.y *= P->k0)) - EPS <= 1.) {
+        if (t >= 1.)
+            lp.phi = xy.y < 0. ? -M_HALFPI : M_HALFPI;
+        else
+            lp.phi = asin(xy.y);
+        lp.lam = xy.x / P->k0;
+    } else {
+        proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+        return lp;
+    }
+    return (lp);
+}
+
+static PJ *destructor (PJ *P, int errlev) {                        /* Destructor */
+    if (nullptr==P)
+        return nullptr;
+
+    if (nullptr==P->opaque)
+        return pj_default_destructor (P, errlev);
+
+    pj_dealloc (static_cast<struct pj_opaque*>(P->opaque)->apa);
+    return pj_default_destructor (P, errlev);
+}
+
+
+PJ *PROJECTION(cea) {
+    double t = 0.0;
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+    if (nullptr==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = Q;
+    P->destructor = destructor;
+
+
+    if (pj_param(P->ctx, P->params, "tlat_ts").i) {
+        P->k0 = cos(t = pj_param(P->ctx, P->params, "rlat_ts").f);
+        if (P->k0 < 0.)
+            return pj_default_destructor (P, PJD_ERR_LAT_TS_LARGER_THAN_90);
+    }
+    if (P->es != 0.0) {
+        t = sin(t);
+        P->k0 /= sqrt(1. - P->es * t * t);
+        P->e = sqrt(P->es);
+        if (!(Q->apa = pj_authset(P->es)))
+            return pj_default_destructor(P, ENOMEM);
+
+        Q->qp = pj_qsfn(1., P->e, P->one_es);
+        P->inv = e_inverse;
+        P->fwd = e_forward;
+    } else {
+        P->inv = s_inverse;
+        P->fwd = s_forward;
+    }
+
+    return P;
+}