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src/Source/LibWebP/src/mux/mux.anim_encode.c  view on Meta::CPAN

  return enc;  // All OK.

 Err:
  WebPAnimEncoderDelete(enc);
  return NULL;
}

// Release the data contained by 'encoded_frame'.
static void FrameRelease(EncodedFrame* const encoded_frame) {
  if (encoded_frame != NULL) {
    WebPDataClear(&encoded_frame->sub_frame_.bitstream);
    WebPDataClear(&encoded_frame->key_frame_.bitstream);
    memset(encoded_frame, 0, sizeof(*encoded_frame));
  }
}

void WebPAnimEncoderDelete(WebPAnimEncoder* enc) {
  if (enc != NULL) {;
    WebPPictureFree(&enc->curr_canvas_copy_);
    WebPPictureFree(&enc->prev_canvas_);
    WebPPictureFree(&enc->prev_canvas_disposed_);
    if (enc->encoded_frames_ != NULL) {
      size_t i;
      for (i = 0; i < enc->size_; ++i) {
        FrameRelease(&enc->encoded_frames_[i]);
      }
      WebPSafeFree(enc->encoded_frames_);
    }
    WebPMuxDelete(enc->mux_);
    WebPSafeFree(enc);
  }
}

// -----------------------------------------------------------------------------
// Frame addition.

// Returns cached frame at the given 'position'.
static EncodedFrame* GetFrame(const WebPAnimEncoder* const enc,
                              size_t position) {
  assert(enc->start_ + position < enc->size_);
  return &enc->encoded_frames_[enc->start_ + position];
}

// Returns true if 'length' number of pixels in 'src' and 'dst' are identical,
// assuming the given step sizes between pixels.
static WEBP_INLINE int ComparePixels(const uint32_t* src, int src_step,
                                     const uint32_t* dst, int dst_step,
                                     int length) {
  assert(length > 0);
  while (length-- > 0) {
    if (*src != *dst) {
      return 0;
    }
    src += src_step;
    dst += dst_step;
  }
  return 1;
}

// Assumes that an initial valid guess of change rectangle 'rect' is passed.
static void MinimizeChangeRectangle(const WebPPicture* const src,
                                    const WebPPicture* const dst,
                                    FrameRect* const rect) {
  int i, j;
  // Sanity checks.
  assert(src->width == dst->width && src->height == dst->height);
  assert(rect->x_offset_ + rect->width_ <= dst->width);
  assert(rect->y_offset_ + rect->height_ <= dst->height);

  // Left boundary.
  for (i = rect->x_offset_; i < rect->x_offset_ + rect->width_; ++i) {
    const uint32_t* const src_argb =
        &src->argb[rect->y_offset_ * src->argb_stride + i];
    const uint32_t* const dst_argb =
        &dst->argb[rect->y_offset_ * dst->argb_stride + i];
    if (ComparePixels(src_argb, src->argb_stride, dst_argb, dst->argb_stride,
                      rect->height_)) {
      --rect->width_;  // Redundant column.
      ++rect->x_offset_;
    } else {
      break;
    }
  }
  if (rect->width_ == 0) goto End;

  // Right boundary.
  for (i = rect->x_offset_ + rect->width_ - 1; i >= rect->x_offset_; --i) {
    const uint32_t* const src_argb =
        &src->argb[rect->y_offset_ * src->argb_stride + i];
    const uint32_t* const dst_argb =
        &dst->argb[rect->y_offset_ * dst->argb_stride + i];
    if (ComparePixels(src_argb, src->argb_stride, dst_argb, dst->argb_stride,
                      rect->height_)) {
      --rect->width_;  // Redundant column.
    } else {
      break;
    }
  }
  if (rect->width_ == 0) goto End;

  // Top boundary.
  for (j = rect->y_offset_; j < rect->y_offset_ + rect->height_; ++j) {
    const uint32_t* const src_argb =
        &src->argb[j * src->argb_stride + rect->x_offset_];
    const uint32_t* const dst_argb =
        &dst->argb[j * dst->argb_stride + rect->x_offset_];
    if (ComparePixels(src_argb, 1, dst_argb, 1, rect->width_)) {
      --rect->height_;  // Redundant row.
      ++rect->y_offset_;
    } else {
      break;
    }
  }
  if (rect->height_ == 0) goto End;

  // Bottom boundary.
  for (j = rect->y_offset_ + rect->height_ - 1; j >= rect->y_offset_; --j) {
    const uint32_t* const src_argb =
        &src->argb[j * src->argb_stride + rect->x_offset_];
    const uint32_t* const dst_argb =
        &dst->argb[j * dst->argb_stride + rect->x_offset_];
    if (ComparePixels(src_argb, 1, dst_argb, 1, rect->width_)) {
      --rect->height_;  // Redundant row.
    } else {
      break;
    }
  }
  if (rect->height_ == 0) goto End;

  if (rect->width_ == 0 || rect->height_ == 0) {
 End:
    // TODO(later): This rare case can happen for a bad GIF. In such a case, the
    // frame should not be encoded at all and the duration of prev frame should
    // be increased instead. For now, we just create a 1x1 frame at zero offset.
    rect->x_offset_ = 0;
    rect->y_offset_ = 0;
    rect->width_ = 1;
    rect->height_ = 1;
  }
}

// Snap rectangle to even offsets (and adjust dimensions if needed).
static WEBP_INLINE void SnapToEvenOffsets(FrameRect* const rect) {
  rect->width_ += (rect->x_offset_ & 1);
  rect->height_ += (rect->y_offset_ & 1);
  rect->x_offset_ &= ~1;
  rect->y_offset_ &= ~1;
}

// Given previous and current canvas, picks the optimal rectangle for the
// current frame. The initial guess for 'rect' will be the full canvas.
static int GetSubRect(const WebPPicture* const prev_canvas,
                      const WebPPicture* const curr_canvas, int is_key_frame,
                      int is_first_frame, FrameRect* const rect,
                      WebPPicture* const sub_frame) {
  rect->x_offset_ = 0;
  rect->y_offset_ = 0;
  rect->width_ = curr_canvas->width;
  rect->height_ = curr_canvas->height;
  if (!is_key_frame || is_first_frame) {  // Optimize frame rectangle.
    // Note: This behaves as expected for first frame, as 'prev_canvas' is
    // initialized to a fully transparent canvas in the beginning.
    MinimizeChangeRectangle(prev_canvas, curr_canvas, rect);
  }
  SnapToEvenOffsets(rect);

  return WebPPictureView(curr_canvas, rect->x_offset_, rect->y_offset_,
                         rect->width_, rect->height_, sub_frame);
}

// TODO: Also used in picture.c. Move to a common location?
// Copy width x height pixels from 'src' to 'dst' honoring the strides.
static void CopyPlane(const uint8_t* src, int src_stride,
                      uint8_t* dst, int dst_stride, int width, int height) {
  while (height-- > 0) {
    memcpy(dst, src, width);
    src += src_stride;
    dst += dst_stride;
  }
}

// Copy pixels from 'src' to 'dst' honoring strides. 'src' and 'dst' are assumed
// to be already allocated.
static void CopyPixels(const WebPPicture* const src, WebPPicture* const dst) {
  assert(src->width == dst->width && src->height == dst->height);
  assert(src->use_argb && dst->use_argb);
  CopyPlane((uint8_t*)src->argb, 4 * src->argb_stride, (uint8_t*)dst->argb,
            4 * dst->argb_stride, 4 * src->width, src->height);
}

static void DisposeFrameRectangle(int dispose_method,
                                  const FrameRect* const rect,
                                  WebPPicture* const curr_canvas) {
  assert(rect != NULL);
  if (dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
    WebPUtilClearPic(curr_canvas, rect);
  }
}

static uint32_t RectArea(const FrameRect* const rect) {
  return (uint32_t)rect->width_ * rect->height_;
}

static int IsBlendingPossible(const WebPPicture* const src,
                              const WebPPicture* const dst,
                              const FrameRect* const rect) {
  int i, j;
  assert(src->width == dst->width && src->height == dst->height);
  assert(rect->x_offset_ + rect->width_ <= dst->width);
  assert(rect->y_offset_ + rect->height_ <= dst->height);
  for (j = rect->y_offset_; j < rect->y_offset_ + rect->height_; ++j) {