[telemetry] Implement per-pixel algorithms in Bitmap as a C++ extension.

tools/telemetry/telemetry/core/bitmaptools/bitmaptools.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <Python.h>
+#include <string.h>
+
+
+struct Box {
+  Box() : left(), top(), right(), bottom() {}
+
+  bool ParseArg(PyObject* obj) {
+    int width;
+    int height;
+    if (!PyArg_ParseTuple(obj, "iiii", &left, &top, &width, &height))
+      return false;
+    if (left < 0 || top < 0 || width < 0 || height < 0) {
+      PyErr_SetString(PyExc_ValueError, "Box dimensions must be non-negative.");
+      return false;
+    }
+    right = left + width;
+    bottom = top + height;
+    return true;
+  }
+
+  PyObject* MakeObject() const {
+    if (right <= left || bottom <= top)
+      return Py_None;
+    return Py_BuildValue("iiii", left, top, right - left, bottom - top);
+  }
+
+  void Union(int x, int y) {
+    if (left > x) left = x;
+    if (right <= x) right = x + 1;
+    if (top > y) top = y;
+    if (bottom <= y) bottom = y + 1;
+  }
+
+  int width() const { return right - left; }
+  int height() const { return bottom - top; }
+
+  int left;
+  int top;
+  int right;
+  int bottom;
+};
+
+
+// Represents a bitmap buffer with a crop box.
+struct Bitmap {
+  Bitmap() {}
+
+  ~Bitmap() {
+    if (pixels.buf)
+      PyBuffer_Release(&pixels);
+  }
+
+  bool ParseArg(PyObject* obj) {
+    int width;
+    int bpp;
+    PyObject* box_object;
+    if (!PyArg_ParseTuple(obj, "s*iiO", &pixels, &width, &bpp, &box_object))
+      return false;
+    if (width <= 0 || bpp <= 0) {
+      PyErr_SetString(PyExc_ValueError, "Width and bpp must be positive.");
+      return false;
+    }
+
+    row_stride = width * bpp;
+    pixel_stride = bpp;
+    total_size = pixels.len;
+    row_size = row_stride;
+
+    if (pixels.len % row_stride != 0) {
+      PyErr_SetString(PyExc_ValueError, "Length must be a multiple of width "
+                                        "and bpp.");
+      return false;
+    }
+
+    if (!box.ParseArg(box_object))
+      return false;
+
+    if (box.bottom * row_stride > total_size ||
+        box.right * pixel_stride > row_size) {
+      PyErr_SetString(PyExc_ValueError, "Crop box overflows the bitmap.");
+      return false;
+    }
+
+    total_size = (box.bottom - box.top) * row_stride;
+    row_size = (box.right - box.left) * pixel_stride;
+    data = reinterpret_cast<const unsigned char*>(pixels.buf) +
+        box.top * row_stride + box.left * pixel_stride;
+    return true;
+  }
+
+  Py_buffer pixels;
+  Box box;
+  // Points at the top-left pixel in |pixels.buf|.
+  const unsigned char* data;
+  // These counts are in bytes.
+  int row_stride;
+  int pixel_stride;
+  int total_size;
+  int row_size;
+};
+
+
+static
+PyObject* Histogram(PyObject* self, PyObject* bmp_object) {
+  Bitmap bmp;
+  if (!bmp.ParseArg(bmp_object))
+    return NULL;
+
+  const int kLength = 3 * 256;
+  int counts[kLength] = {};
+
+  for (const unsigned char* row = bmp.data; row < bmp.data + bmp.total_size;
+       row += bmp.row_stride) {
+    for (const unsigned char* pixel = row; pixel < row + bmp.row_size;
+       pixel += bmp.pixel_stride) {
+      ++(counts[256 * 0 + pixel[0]]);
+      ++(counts[256 * 1 + pixel[1]]);
+      ++(counts[256 * 2 + pixel[2]]);
+    }
+  }
+
+  PyObject* list = PyList_New(kLength);
+  if (!list)
+    return NULL;
+
+  for (int i = 0; i < kLength; ++i)
+    PyList_SetItem(list, i, PyInt_FromLong(counts[i]));
+
+  return list;
+}
+
+
+static inline
+bool PixelsEqual(const unsigned char* pixel1, const unsigned char* pixel2,
+                 int tolerance) {
+  // Note: this works for both RGB and RGBA. Alpha channel is ignored.
+  return (abs(pixel1[0] - pixel2[0]) <= tolerance) &&
+         (abs(pixel1[1] - pixel2[1]) <= tolerance) &&
+         (abs(pixel1[2] - pixel2[2]) <= tolerance);
+}
+
+
+static inline
+bool PixelsEqual(const unsigned char* pixel, int color, int tolerance) {
+  unsigned char pixel2[3] = { color >> 16, color >> 8, color };
+  return PixelsEqual(pixel, pixel2, tolerance);
+}
+
+
+static
+PyObject* Equal(PyObject* self, PyObject* args) {
+  PyObject* bmp_obj1;
+  PyObject* bmp_obj2;
+  int tolerance;
+  if (!PyArg_ParseTuple(args, "OOi", &bmp_obj1, &bmp_obj2, &tolerance))
+    return NULL;
+
+  Bitmap bmp1, bmp2;
+  if (!bmp1.ParseArg(bmp_obj1) || !bmp2.ParseArg(bmp_obj2))
+    return NULL;
+
+  if (bmp1.box.width() != bmp2.box.width() ||
+      bmp1.box.height() != bmp2.box.height()) {
+    PyErr_SetString(PyExc_ValueError, "Bitmap dimensions don't match.");
+    return NULL;
+  }
+
+  bool simple_match = (tolerance == 0) &&
+                      (bmp1.pixel_stride == 3) &&
+                      (bmp2.pixel_stride == 3);
+  for (const unsigned char *row1 = bmp1.data, *row2 = bmp2.data;
+       row1 < bmp1.data + bmp1.total_size;
+       row1 += bmp1.row_stride, row2 += bmp2.row_stride) {
+    if (simple_match) {
+      if (memcmp(row1, row2, bmp1.row_size) != 0)
+        return Py_False;
+      continue;
+    }
+    for (const unsigned char *pixel1 = row1, *pixel2 = row2;
+         pixel1 < row1 + bmp1.row_size;
+         pixel1 += bmp1.pixel_stride, pixel2 += bmp2.pixel_stride) {
+      if (!PixelsEqual(pixel1, pixel2, tolerance))
+        return Py_False;
+    }
+  }
+
+  return Py_True;
+}
+
+
+static
+PyObject* BoundingBox(PyObject* self, PyObject* args) {
+  PyObject* bmp_object;
+  int color;
+  int tolerance;
+  if (!PyArg_ParseTuple(args, "Oii", &bmp_object, &color, &tolerance))
+    return NULL;
+
+  Bitmap bmp;
+  if (!bmp.ParseArg(bmp_object))
+    return NULL;
+
+  Box box;
+  box.left = bmp.pixels.len;
+  box.top = bmp.pixels.len;
+  box.right = 0;
+  box.bottom = 0;
+
+  int count = 0;
+  int y = 0;
+  for (const unsigned char* row = bmp.data; row < bmp.data + bmp.total_size;
+       row += bmp.row_stride, ++y) {
+    int x = 0;
+    for (const unsigned char* pixel = row; pixel < row + bmp.row_size;
+         pixel += bmp.pixel_stride, ++x) {
+      if (!PixelsEqual(pixel, color, tolerance))
+        continue;
+      box.Union(x, y);
+      ++count;
+    }
+  }
+
+  return Py_BuildValue("Oi", box.MakeObject(), count);
+}
+
+
+static
+PyObject* Crop(PyObject* self, PyObject* bmp_object) {
+  Bitmap bmp;
+  if (!bmp.ParseArg(bmp_object))
+    return NULL;
+
+  int out_size = bmp.row_size * bmp.box.height();
+  unsigned char* out = new unsigned char[out_size];
+  unsigned char* dst = out;
+  for (const unsigned char* row = bmp.data;
+       row < bmp.data + bmp.total_size;
+       row += bmp.row_stride, dst += bmp.row_size) {
+    // No change in pixel_stride, so we can copy whole rows.
+    memcpy(dst, row, bmp.row_size);
+  }
+
+  PyObject* result = Py_BuildValue("s#", out, out_size);
+  delete[] out;
+  return result;
+}
+
+
+static PyMethodDef module_methods[] = {
+  {"Histogram", Histogram, METH_O,
+    "Calculates histogram of bitmap colors. Returns a list of 3x256 ints."},
+  {"Equal", Equal, METH_VARARGS,
+    "Checks if the two bmps are equal."},
+  {"BoundingBox", BoundingBox, METH_VARARGS,
+    "Calculates bounding box of matching color."},
+  {"Crop", Crop, METH_O,
+    "Crops the bmp to crop box."},
+  {NULL, NULL, 0, NULL}  /* sentinel */
+};
+
+PyMODINIT_FUNC initbitmaptools(void) {
+  Py_InitModule("bitmaptools", module_methods);
+}