From 61a530742f70e59d7fbd7c35a22292176ca554fa Mon Sep 17 00:00:00 2001
From: "Philip P. Moltmann" <moltmann@google.com>
Date: Tue, 31 May 2016 14:07:54 -0700
Subject: [PATCH] Use SkMatrix to compute pdf transformation.

Bug: 28051413
Change-Id: Id17db12801a33955426d7e01d0af950b1c6468cf
---
 core/jni/android/graphics/pdf/PdfEditor.cpp   | 35 ++++++++++---------
 core/jni/android/graphics/pdf/PdfRenderer.cpp | 16 +++++----
 2 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/core/jni/android/graphics/pdf/PdfEditor.cpp b/core/jni/android/graphics/pdf/PdfEditor.cpp
index 0468b644862db..21f3c46b4c3d2 100644
--- a/core/jni/android/graphics/pdf/PdfEditor.cpp
+++ b/core/jni/android/graphics/pdf/PdfEditor.cpp
@@ -22,7 +22,6 @@
 #include "fpdfview.h"
 #include "fpdf_edit.h"
 #include "fpdf_save.h"
-#include "fsdk_rendercontext.h"
 #include "fpdf_transformpage.h"
 #pragma GCC diagnostic pop
 
@@ -176,7 +175,7 @@ static void nativeSetTransformAndClip(JNIEnv* env, jclass thiz, jlong documentPt
         jlong transformPtr, jint clipLeft, jint clipTop, jint clipRight, jint clipBottom) {
     FPDF_DOCUMENT document = reinterpret_cast<FPDF_DOCUMENT>(documentPtr);
 
-    CPDF_Page* page = (CPDF_Page*) FPDF_LoadPage(document, pageIndex);
+    FPDF_PAGE* page = (FPDF_PAGE*) FPDF_LoadPage(document, pageIndex);
     if (!page) {
         jniThrowException(env, "java/lang/IllegalStateException",
                 "cannot open page");
@@ -193,30 +192,32 @@ static void nativeSetTransformAndClip(JNIEnv* env, jclass thiz, jlong documentPt
         return;
     }
 
-    CFX_Matrix matrix;
 
-    SkMatrix* skTransform = reinterpret_cast<SkMatrix*>(transformPtr);
+    // PDF's coordinate system origin is left-bottom while in graphics it
+    // is the top-left. So, translate the PDF coordinates to ours.
+    SkMatrix reflectOnX = SkMatrix::MakeScale(1, -1);
+    SkMatrix moveUp = SkMatrix::MakeTrans(0, FPDF_GetPageHeight(page));
+    SkMatrix coordinateChange = SkMatrix::Concat(moveUp, reflectOnX);
+
+    // Apply the transformation what was created in our coordinates.
+    SkMatrix matrix = SkMatrix::Concat(*reinterpret_cast<SkMatrix*>(transformPtr),
+            coordinateChange);
+
+    // Translate the result back to PDF coordinates.
+    matrix.setConcat(coordinateChange, matrix);
 
     SkScalar transformValues[6];
-    if (!skTransform->asAffine(transformValues)) {
+    if (!matrix.asAffine(transformValues)) {
         jniThrowException(env, "java/lang/IllegalArgumentException",
                 "transform matrix has perspective. Only affine matrices are allowed.");
         return;
     }
 
-    // PDF's coordinate system origin is left-bottom while in graphics it
-    // is the top-left. So, translate the PDF coordinates to ours.
-    matrix.Set(1, 0, 0, -1, 0, page->GetPageHeight());
+    FS_MATRIX transform = {transformValues[SkMatrix::kAScaleX], transformValues[SkMatrix::kASkewY],
+                           transformValues[SkMatrix::kASkewX], transformValues[SkMatrix::kAScaleY],
+                           transformValues[SkMatrix::kATransX],
+                           transformValues[SkMatrix::kATransY]};
 
-    // Apply the transformation what was created in our coordinates.
-    matrix.Concat(transformValues[SkMatrix::kAScaleX], transformValues[SkMatrix::kASkewY],
-            transformValues[SkMatrix::kASkewX], transformValues[SkMatrix::kAScaleY],
-            transformValues[SkMatrix::kATransX], transformValues[SkMatrix::kATransY]);
-
-    // Translate the result back to PDF coordinates.
-    matrix.Concat(1, 0, 0, -1, 0, page->GetPageHeight());
-
-    FS_MATRIX transform = {matrix.a, matrix.b, matrix.c, matrix.d, matrix.e, matrix.f};
     FS_RECTF clip = {(float) clipLeft, (float) clipTop, (float) clipRight, (float) clipBottom};
 
     FPDFPage_TransFormWithClip(page, &transform, &clip);
diff --git a/core/jni/android/graphics/pdf/PdfRenderer.cpp b/core/jni/android/graphics/pdf/PdfRenderer.cpp
index 43550ac9ed72b..3ef2c027f85ab 100644
--- a/core/jni/android/graphics/pdf/PdfRenderer.cpp
+++ b/core/jni/android/graphics/pdf/PdfRenderer.cpp
@@ -212,19 +212,23 @@ static void renderPageBitmap(FPDF_BITMAP bitmap, FPDF_PAGE page, int destLeft, i
     } else {
         // PDF's coordinate system origin is left-bottom while
         // in graphics it is the top-left, so remap the origin.
-        matrix.Set(1, 0, 0, -1, 0, pPage->GetPageHeight());
+        SkMatrix reflectOnX = SkMatrix::MakeScale(1, -1);
+        SkMatrix moveUp = SkMatrix::MakeTrans(0, FPDF_GetPageHeight(page));
+        SkMatrix m = SkMatrix::Concat(moveUp, reflectOnX);
+
+        // Concatenate transformation and origin transformation
+        m.setConcat(*transform, m);
 
         SkScalar transformValues[6];
-        if (transform->asAffine(transformValues)) {
-            matrix.Concat(transformValues[SkMatrix::kAScaleX], transformValues[SkMatrix::kASkewY],
-                    transformValues[SkMatrix::kASkewX], transformValues[SkMatrix::kAScaleY],
-                    transformValues[SkMatrix::kATransX], transformValues[SkMatrix::kATransY]);
-        } else {
+        if (!m.asAffine(transformValues)) {
             // Already checked for a return value of false in the caller, so this should never
             // happen.
             ALOGE("Error rendering page!");
         }
 
+        matrix = {transformValues[SkMatrix::kAScaleX], transformValues[SkMatrix::kASkewY],
+                  transformValues[SkMatrix::kASkewX], transformValues[SkMatrix::kAScaleY],
+                  transformValues[SkMatrix::kATransX], transformValues[SkMatrix::kATransY]};
     }
     pageContext->AppendObjectList(pPage, &matrix);