Add a map homogenous points to SkMatrix

tests/MatrixTest.cpp

Index: tests/MatrixTest.cpp
diff --git a/tests/MatrixTest.cpp b/tests/MatrixTest.cpp
index 2f16d656619bf0c881ad9a85f71285cb30196996..16801d1a76c5caf4d2670a4e738fd7c16187c476 100644
--- a/tests/MatrixTest.cpp
+++ b/tests/MatrixTest.cpp
@@ -592,6 +592,141 @@ static void test_matrix_decomposition(skiatest::Reporter* reporter) {
     REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
 }
 
+// For test_matrix_homogeneous, below.
+static bool scalar_array_nearly_equal_relative(const SkScalar a[], const SkScalar b[], int count) {
+    for (int i = 0; i < count; ++i) {
+        if (!scalar_nearly_equal_relative(a[i], b[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
+// For test_matrix_homogeneous, below.
+// Maps a single triple in src using m and compares results to those in dst
+static bool naive_homogeneous_mapping(const SkMatrix& m, const SkScalar src[3],
+                                      const SkScalar dst[3]) {
+    SkScalar res[3];
+    res[0] = src[0] * m[0] + src[1] * m[1] + src[2] * m[2];
+    res[1] = src[0] * m[3] + src[1] * m[4] + src[2] * m[5];
+    res[2] = src[0] * m[6] + src[1] * m[7] + src[2] * m[8];
+    return scalar_array_nearly_equal_relative(res, dst, 3);
+}
+
+static void test_matrix_homogeneous(skiatest::Reporter* reporter) {
+    SkMatrix mat;
+
+    const float kRotation0 = 15.5f;
+    const float kRotation1 = -50.f;
+    const float kScale0 = 5000.f;
+
+    const int kTripleCount = 1000;
+    const int kMatrixCount = 1000;
+    SkRandom rand;
+
+    SkScalar randTriples[3*kTripleCount];
+    for (int i = 0; i < 3*kTripleCount; ++i) {
+        randTriples[i] = rand.nextRangeF(-3000.f, 3000.f);
+    }
+
+    SkMatrix mats[kMatrixCount];
+    for (int i = 0; i < kMatrixCount; ++i) {
+        for (int j = 0; j < 9; ++j) {
+            mats[i].set(j, rand.nextRangeF(-3000.f, 3000.f));
+        }
+    }
+
+    // identity
+    {
+    mat.reset();
+    SkScalar dst[3*kTripleCount];
+    mat.mapHomogeneousPoints(dst, randTriples, kTripleCount);
+    REPORTER_ASSERT(reporter, scalar_array_nearly_equal_relative(randTriples, dst, kTripleCount*3));
+    }
+
+    // zero matrix
+    {
+    mat.setAll(0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f);
+    SkScalar dst[3*kTripleCount];
+    mat.mapHomogeneousPoints(dst, randTriples, kTripleCount);
+    SkScalar zeros[3] = {0.f, 0.f, 0.f};
+    for (int i = 0; i < kTripleCount; ++i) {
+        REPORTER_ASSERT(reporter, scalar_array_nearly_equal_relative(&dst[i*3], zeros, 3));
+    }
+    }
+
+    // zero point
+    {
+    SkScalar zeros[3] = {0.f, 0.f, 0.f};
+    for (int i = 0; i < kMatrixCount; ++i) {
+        SkScalar dst[3];
+        mats[i].mapHomogeneousPoints(dst, zeros, 1);
+        REPORTER_ASSERT(reporter, scalar_array_nearly_equal_relative(dst, zeros, 3));
+    }
+    }
+
+    // doesn't crash with null dst, src, count == 0
+    {
+    mats[0].mapHomogeneousPoints(NULL, NULL, 0);
+    }
+
+    // uniform scale of point
+    {
+    mat.setScale(kScale0, kScale0);
+    SkScalar dst[3];
+    SkScalar src[3] = {randTriples[0], randTriples[1], 1.f};
+    SkPoint pnt;
+    pnt.set(src[0], src[1]);
+    mat.mapHomogeneousPoints(dst, src, 1);
+    mat.mapPoints(&pnt, &pnt, 1);
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[0], pnt.fX));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[1], pnt.fY));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[2], SK_Scalar1));
+    }
+
+    // rotation of point
+    {
+    mat.setRotate(kRotation0);
+    SkScalar dst[3];
+    SkScalar src[3] = {randTriples[0], randTriples[1], 1.f};
+    SkPoint pnt;
+    pnt.set(src[0], src[1]);
+    mat.mapHomogeneousPoints(dst, src, 1);
+    mat.mapPoints(&pnt, &pnt, 1);
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[0], pnt.fX));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[1], pnt.fY));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[2], SK_Scalar1));
+    }
+
+    // rotation, scale, rotation of point
+    {
+    mat.setRotate(kRotation1);
+    mat.postScale(kScale0, kScale0);
+    mat.postRotate(kRotation0);
+    SkScalar dst[3];
+    SkScalar src[3] = {randTriples[0], randTriples[1], 1.f};
+    SkPoint pnt;
+    pnt.set(src[0], src[1]);
+    mat.mapHomogeneousPoints(dst, src, 1);
+    mat.mapPoints(&pnt, &pnt, 1);
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[0], pnt.fX));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[1], pnt.fY));
+    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(dst[2], SK_Scalar1));
+    }
+
+    // compare with naive approach
+    {
+    for (int i = 0; i < kMatrixCount; ++i) {
+        for (int j = 0; j < kTripleCount; ++j) {
+            SkScalar dst[3];
+            mats[i].mapHomogeneousPoints(dst, &randTriples[j*3], 1);
+            REPORTER_ASSERT(reporter, naive_homogeneous_mapping(mats[i], &randTriples[j*3], dst));
+        }
+    }
+    }
+
+}
+
 static void TestMatrix(skiatest::Reporter* reporter) {
     SkMatrix    mat, inverse, iden1, iden2;
 
@@ -713,6 +848,7 @@ static void TestMatrix(skiatest::Reporter* reporter) {
     test_matrix_is_similarity(reporter);
     test_matrix_recttorect(reporter);
     test_matrix_decomposition(reporter);
+    test_matrix_homogeneous(reporter);
 }
 
 #include "TestClassDef.h"