Android: Add support for cropping textures

webrtc/api/java/jni/native_handle_impl.cc

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 41 matching lines @@
       const float ROTATE_270[16] =
           { -a[4], -a[5], -a[6], -a[7],
             a[0], a[1], a[2], a[3],
             a[8], a[9], a[10], a[11],
             a[4] + a[12], a[5] + a[13], a[6] + a[14], a[7] + a[15]};
         memcpy(a, ROTATE_270, sizeof(ROTATE_270));
     } break;
   }
 }
 
+// Calculates result = a * b, in column-major order.
+void MultiplyMatrix(const float a[16], const float b[16], float result[16]) {
+  for (int i = 0; i < 4; ++i) {
+    for (int j = 0; j < 4; ++j) {
+      float sum = 0;
+      for (int k = 0; k < 4; ++k) {
+        sum += a[k * 4 + j] * b[i * 4 + k];
+      }
+      result[i * 4 + j] = sum;
+    }
+  }
+}
+
+// Center crop by keeping xFraction of the width and yFraction of the height,
+// so e.g. cropping from 640x480 to 640x360 would use
+// xFraction=1, yFraction=360/480.
+void CropMatrix(float a[16], float xFraction, float yFraction) {
+  // Move cropped area to the center of the frame by offsetting half the
+  // removed area.
+  const float xOffset = (1 - xFraction) / 2;
+  const float yOffset = (1 - yFraction) / 2;
+  const float crop_matrix[16] = {
+    xFraction, 0, 0, 0,
+    0, yFraction, 0, 0,
+    0, 0, 1, 0,
+    xOffset, yOffset, 0, 1};
+  float mul_result[16];
+  MultiplyMatrix(crop_matrix, a, mul_result);
+  memcpy(a, mul_result, sizeof(mul_result));
+}
+
 }  // anonymouse namespace
 
 namespace webrtc_jni {
 
 // Aligning pointer to 64 bytes for improved performance, e.g. use SIMD.
 static const int kBufferAlignment = 64;
 
 NativeHandleImpl::NativeHandleImpl(JNIEnv* jni,
                                    jint j_oes_texture_id,
                                    jfloatArray j_transform_matrix)
@@ skipping 67 matching lines @@
   jni->CallVoidMethod(surface_texture_helper_,
                       transform_mid,
                       byte_buffer, width(), height(), stride,
                       native_handle_.oes_texture_id, sampling_matrix);
   CHECK_EXCEPTION(jni) << "textureToYUV throwed an exception";
 
   return copy;
 }
 
 rtc::scoped_refptr<AndroidTextureBuffer>
-AndroidTextureBuffer::ScaleAndRotate(int dst_widht,
-                                     int dst_height,
-                                     webrtc::VideoRotation rotation) {
-  if (width() == dst_widht && height() == dst_height &&
+AndroidTextureBuffer::CropScaleAndRotate(int cropped_width,
+                                         int cropped_height,
+                                         int dst_width,
+                                         int dst_height,
+                                         webrtc::VideoRotation rotation) {
+  if (cropped_width == dst_width && cropped_height == dst_height &&
+      width() == dst_width && height() == dst_height &&
       rotation == webrtc::kVideoRotation_0) {
     return this;
   }
-  int rotated_width = (rotation % 180 == 0) ? dst_widht : dst_height;
-  int rotated_height = (rotation % 180 == 0) ? dst_height : dst_widht;
+  int rotated_width = (rotation % 180 == 0) ? dst_width : dst_height;
+  int rotated_height = (rotation % 180 == 0) ? dst_height : dst_width;
 
   // Here we use Bind magic to add a reference count to |this| until the newly
   // created AndroidTextureBuffer is destructed
   rtc::scoped_refptr<AndroidTextureBuffer> buffer(
       new rtc::RefCountedObject<AndroidTextureBuffer>(
           rotated_width, rotated_height, native_handle_,
           surface_texture_helper_, rtc::KeepRefUntilDone(this)));
 
+  if (cropped_width != width() || cropped_height != height()) {
+    CropMatrix(buffer->native_handle_.sampling_matrix,
+               cropped_width / static_cast<float>(width()),
+               cropped_height / static_cast<float>(height()));
+  }
   RotateMatrix(buffer->native_handle_.sampling_matrix, rotation);
   return buffer;
 }
 
 }  // namespace webrtc_jni