libwebp: update to 0.5.0

third_party/libwebp/demux/anim_decode.c

+// Copyright 2015 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING 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.
+// -----------------------------------------------------------------------------
+//
+//  AnimDecoder implementation.
+//
+
+#ifdef HAVE_CONFIG_H
+#include "../webp/config.h"
+#endif
+
+#include <assert.h>
+#include <string.h>
+
+#include "../utils/utils.h"
+#include "../webp/decode.h"
+#include "../webp/demux.h"
+
+#define NUM_CHANNELS 4
+
+typedef void (*BlendRowFunc)(uint32_t* const, const uint32_t* const, int);
+static void BlendPixelRowNonPremult(uint32_t* const src,
+                                    const uint32_t* const dst, int num_pixels);
+static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst,
+                                 int num_pixels);
+
+struct WebPAnimDecoder {
+  WebPDemuxer* demux_;             // Demuxer created from given WebP bitstream.
+  WebPDecoderConfig config_;       // Decoder config.
+  // Note: we use a pointer to a function blending multiple pixels at a time to
+  // allow possible inlining of per-pixel blending function.
+  BlendRowFunc blend_func_;        // Pointer to the chose blend row function.
+  WebPAnimInfo info_;              // Global info about the animation.
+  uint8_t* curr_frame_;            // Current canvas (not disposed).
+  uint8_t* prev_frame_disposed_;   // Previous canvas (properly disposed).
+  int prev_frame_timestamp_;       // Previous frame timestamp (milliseconds).
+  WebPIterator prev_iter_;         // Iterator object for previous frame.
+  int prev_frame_was_keyframe_;    // True if previous frame was a keyframe.
+  int next_frame_;                 // Index of the next frame to be decoded
+                                   // (starting from 1).
+};
+
+static void DefaultDecoderOptions(WebPAnimDecoderOptions* const dec_options) {
+  dec_options->color_mode = MODE_RGBA;
+  dec_options->use_threads = 0;
+}
+
+int WebPAnimDecoderOptionsInitInternal(WebPAnimDecoderOptions* dec_options,
+                                       int abi_version) {
+  if (dec_options == NULL ||
+      WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) {
+    return 0;
+  }
+  DefaultDecoderOptions(dec_options);
+  return 1;
+}
+
+static int ApplyDecoderOptions(const WebPAnimDecoderOptions* const dec_options,
+                               WebPAnimDecoder* const dec) {
+  WEBP_CSP_MODE mode;
+  WebPDecoderConfig* config = &dec->config_;
+  assert(dec_options != NULL);
+
+  mode = dec_options->color_mode;
+  if (mode != MODE_RGBA && mode != MODE_BGRA &&
+      mode != MODE_rgbA && mode != MODE_bgrA) {
+    return 0;
+  }
+  dec->blend_func_ = (mode == MODE_RGBA || mode == MODE_BGRA)
+                         ? &BlendPixelRowNonPremult
+                         : &BlendPixelRowPremult;
+  WebPInitDecoderConfig(config);
+  config->output.colorspace = mode;
+  config->output.is_external_memory = 1;
+  config->options.use_threads = dec_options->use_threads;
+  // Note: config->output.u.RGBA is set at the time of decoding each frame.
+  return 1;
+}
+
+WebPAnimDecoder* WebPAnimDecoderNewInternal(
+    const WebPData* webp_data, const WebPAnimDecoderOptions* dec_options,
+    int abi_version) {
+  WebPAnimDecoderOptions options;
+  WebPAnimDecoder* dec = NULL;
+  if (webp_data == NULL ||
+      WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) {
+    return NULL;
+  }
+
+  // Note: calloc() so that the pointer members are initialized to NULL.
+  dec = (WebPAnimDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
+  if (dec == NULL) goto Error;
+
+  if (dec_options != NULL) {
+    options = *dec_options;
+  } else {
+    DefaultDecoderOptions(&options);
+  }
+  if (!ApplyDecoderOptions(&options, dec)) goto Error;
+
+  dec->demux_ = WebPDemux(webp_data);
+  if (dec->demux_ == NULL) goto Error;
+
+  dec->info_.canvas_width = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_WIDTH);
+  dec->info_.canvas_height = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_HEIGHT);
+  dec->info_.loop_count = WebPDemuxGetI(dec->demux_, WEBP_FF_LOOP_COUNT);
+  dec->info_.bgcolor = WebPDemuxGetI(dec->demux_, WEBP_FF_BACKGROUND_COLOR);
+  dec->info_.frame_count = WebPDemuxGetI(dec->demux_, WEBP_FF_FRAME_COUNT);
+
+  {
+    const int canvas_bytes =
+        dec->info_.canvas_width * NUM_CHANNELS * dec->info_.canvas_height;
+    // Note: calloc() because we fill frame with zeroes as well.
+    dec->curr_frame_ = WebPSafeCalloc(1ULL, canvas_bytes);
+    if (dec->curr_frame_ == NULL) goto Error;
+    dec->prev_frame_disposed_ = WebPSafeCalloc(1ULL, canvas_bytes);
+    if (dec->prev_frame_disposed_ == NULL) goto Error;
+  }
+
+  WebPAnimDecoderReset(dec);
+
+  return dec;
+
+ Error:
+  WebPAnimDecoderDelete(dec);
+  return NULL;
+}
+
+int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec, WebPAnimInfo* info) {
+  if (dec == NULL || info == NULL) return 0;
+  *info = dec->info_;
+  return 1;
+}
+
+// Returns true if the frame covers the full canvas.
+static int IsFullFrame(int width, int height, int canvas_width,
+                       int canvas_height) {
+  return (width == canvas_width && height == canvas_height);
+}
+
+// Clear the canvas to transparent.
+static void ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
+                           uint32_t canvas_height) {
+  memset(buf, 0, canvas_width * NUM_CHANNELS * canvas_height);
+}
+
+// Clear given frame rectangle to transparent.
+static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset,
+                              int y_offset, int width, int height) {
+  int j;
+  assert(width * NUM_CHANNELS <= buf_stride);
+  buf += y_offset * buf_stride + x_offset * NUM_CHANNELS;
+  for (j = 0; j < height; ++j) {
+    memset(buf, 0, width * NUM_CHANNELS);
+    buf += buf_stride;
+  }
+}
+
+// Copy width * height pixels from 'src' to 'dst'.
+static void CopyCanvas(const uint8_t* src, uint8_t* dst,
+                       uint32_t width, uint32_t height) {
+  assert(src != NULL && dst != NULL);
+  memcpy(dst, src, width * NUM_CHANNELS * height);
+}
+
+// Returns true if the current frame is a key-frame.
+static int IsKeyFrame(const WebPIterator* const curr,
+                      const WebPIterator* const prev,
+                      int prev_frame_was_key_frame,
+                      int canvas_width, int canvas_height) {
+  if (curr->frame_num == 1) {
+    return 1;
+  } else if ((!curr->has_alpha || curr->blend_method == WEBP_MUX_NO_BLEND) &&
+             IsFullFrame(curr->width, curr->height,
+                         canvas_width, canvas_height)) {
+    return 1;
+  } else {
+    return (prev->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) &&
+           (IsFullFrame(prev->width, prev->height, canvas_width,
+                        canvas_height) ||
+            prev_frame_was_key_frame);
+  }
+}
+
+
+// Blend a single channel of 'src' over 'dst', given their alpha channel values.
+// 'src' and 'dst' are assumed to be NOT pre-multiplied by alpha.
+static uint8_t BlendChannelNonPremult(uint32_t src, uint8_t src_a,
+                                      uint32_t dst, uint8_t dst_a,
+                                      uint32_t scale, int shift) {
+  const uint8_t src_channel = (src >> shift) & 0xff;
+  const uint8_t dst_channel = (dst >> shift) & 0xff;
+  const uint32_t blend_unscaled = src_channel * src_a + dst_channel * dst_a;
+  assert(blend_unscaled < (1ULL << 32) / scale);
+  return (blend_unscaled * scale) >> 24;
+}
+
+// Blend 'src' over 'dst' assuming they are NOT pre-multiplied by alpha.
+static uint32_t BlendPixelNonPremult(uint32_t src, uint32_t dst) {
+  const uint8_t src_a = (src >> 24) & 0xff;
+
+  if (src_a == 0) {
+    return dst;
+  } else {
+    const uint8_t dst_a = (dst >> 24) & 0xff;
+    // This is the approximate integer arithmetic for the actual formula:
+    // dst_factor_a = (dst_a * (255 - src_a)) / 255.
+    const uint8_t dst_factor_a = (dst_a * (256 - src_a)) >> 8;
+    const uint8_t blend_a = src_a + dst_factor_a;
+    const uint32_t scale = (1UL << 24) / blend_a;
+
+    const uint8_t blend_r =
+        BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 0);
+    const uint8_t blend_g =
+        BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 8);
+    const uint8_t blend_b =
+        BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 16);
+    assert(src_a + dst_factor_a < 256);
+
+    return (blend_r << 0) |
+           (blend_g << 8) |
+           (blend_b << 16) |
+           ((uint32_t)blend_a << 24);
+  }
+}
+
+// Blend 'num_pixels' in 'src' over 'dst' assuming they are NOT pre-multiplied
+// by alpha.
+static void BlendPixelRowNonPremult(uint32_t* const src,
+                                    const uint32_t* const dst, int num_pixels) {
+  int i;
+  for (i = 0; i < num_pixels; ++i) {
+    const uint8_t src_alpha = (src[i] >> 24) & 0xff;
+    if (src_alpha != 0xff) {
+      src[i] = BlendPixelNonPremult(src[i], dst[i]);
+    }
+  }
+}
+
+// Individually multiply each channel in 'pix' by 'scale'.
+static WEBP_INLINE uint32_t ChannelwiseMultiply(uint32_t pix, uint32_t scale) {
+  uint32_t mask = 0x00FF00FF;
+  uint32_t rb = ((pix & mask) * scale) >> 8;
+  uint32_t ag = ((pix >> 8) & mask) * scale;
+  return (rb & mask) | (ag & ~mask);
+}
+
+// Blend 'src' over 'dst' assuming they are pre-multiplied by alpha.
+static uint32_t BlendPixelPremult(uint32_t src, uint32_t dst) {
+  const uint8_t src_a = (src >> 24) & 0xff;
+  return src + ChannelwiseMultiply(dst, 256 - src_a);
+}
+
+// Blend 'num_pixels' in 'src' over 'dst' assuming they are pre-multiplied by
+// alpha.
+static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst,
+                                 int num_pixels) {
+  int i;
+  for (i = 0; i < num_pixels; ++i) {
+    const uint8_t src_alpha = (src[i] >> 24) & 0xff;
+    if (src_alpha != 0xff) {
+      src[i] = BlendPixelPremult(src[i], dst[i]);
+    }
+  }
+}
+
+// Returns two ranges (<left, width> pairs) at row 'canvas_y', that belong to
+// 'src' but not 'dst'. A point range is empty if the corresponding width is 0.
+static void FindBlendRangeAtRow(const WebPIterator* const src,
+                                const WebPIterator* const dst, int canvas_y,
+                                int* const left1, int* const width1,
+                                int* const left2, int* const width2) {
+  const int src_max_x = src->x_offset + src->width;
+  const int dst_max_x = dst->x_offset + dst->width;
+  const int dst_max_y = dst->y_offset + dst->height;
+  assert(canvas_y >= src->y_offset && canvas_y < (src->y_offset + src->height));
+  *left1 = -1;
+  *width1 = 0;
+  *left2 = -1;
+  *width2 = 0;
+
+  if (canvas_y < dst->y_offset || canvas_y >= dst_max_y ||
+      src->x_offset >= dst_max_x || src_max_x <= dst->x_offset) {
+    *left1 = src->x_offset;
+    *width1 = src->width;
+    return;
+  }
+
+  if (src->x_offset < dst->x_offset) {
+    *left1 = src->x_offset;
+    *width1 = dst->x_offset - src->x_offset;
+  }
+
+  if (src_max_x > dst_max_x) {
+    *left2 = dst_max_x;
+    *width2 = src_max_x - dst_max_x;
+  }
+}
+
+int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
+                           uint8_t** buf_ptr, int* timestamp_ptr) {
+  WebPIterator iter;
+  uint32_t width;
+  uint32_t height;
+  int is_key_frame;
+  int timestamp;
+  BlendRowFunc blend_row;
+
+  if (dec == NULL || buf_ptr == NULL || timestamp_ptr == NULL) return 0;
+  if (!WebPAnimDecoderHasMoreFrames(dec)) return 0;
+
+  width = dec->info_.canvas_width;
+  height = dec->info_.canvas_height;
+  blend_row = dec->blend_func_;
+
+  // Get compressed frame.
+  if (!WebPDemuxGetFrame(dec->demux_, dec->next_frame_, &iter)) {
+    return 0;
+  }
+  timestamp = dec->prev_frame_timestamp_ + iter.duration;
+
+  // Initialize.
+  is_key_frame = IsKeyFrame(&iter, &dec->prev_iter_,
+                            dec->prev_frame_was_keyframe_, width, height);
+  if (is_key_frame) {
+    ZeroFillCanvas(dec->curr_frame_, width, height);
+  } else {
+    CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_, width, height);
+  }
+
+  // Decode.
+  {
+    const uint8_t* in = iter.fragment.bytes;
+    const size_t in_size = iter.fragment.size;
+    const size_t out_offset =
+        (iter.y_offset * width + iter.x_offset) * NUM_CHANNELS;
+    WebPDecoderConfig* const config = &dec->config_;
+    WebPRGBABuffer* const buf = &config->output.u.RGBA;
+    buf->stride = NUM_CHANNELS * width;
+    buf->size = buf->stride * iter.height;
+    buf->rgba = dec->curr_frame_ + out_offset;
+
+    if (WebPDecode(in, in_size, config) != VP8_STATUS_OK) {
+      goto Error;
+    }
+  }
+
+  // During the decoding of current frame, we may have set some pixels to be
+  // transparent (i.e. alpha < 255). However, the value of each of these
+  // pixels should have been determined by blending it against the value of
+  // that pixel in the previous frame if blending method of is WEBP_MUX_BLEND.
+  if (iter.frame_num > 1 && iter.blend_method == WEBP_MUX_BLEND &&
+      !is_key_frame) {
+    if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_NONE) {
+      int y;
+      // Blend transparent pixels with pixels in previous canvas.
+      for (y = 0; y < iter.height; ++y) {
+        const size_t offset =
+            (iter.y_offset + y) * width + iter.x_offset;
+        blend_row((uint32_t*)dec->curr_frame_ + offset,
+                  (uint32_t*)dec->prev_frame_disposed_ + offset, iter.width);
+      }
+    } else {
+      int y;
+      assert(dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND);
+      // We need to blend a transparent pixel with its value just after
+      // initialization. That is, blend it with:
+      // * Fully transparent pixel if it belongs to prevRect <-- No-op.
+      // * The pixel in the previous canvas otherwise <-- Need alpha-blending.
+      for (y = 0; y < iter.height; ++y) {
+        const int canvas_y = iter.y_offset + y;
+        int left1, width1, left2, width2;
+        FindBlendRangeAtRow(&iter, &dec->prev_iter_, canvas_y, &left1, &width1,
+                            &left2, &width2);
+        if (width1 > 0) {
+          const size_t offset1 = canvas_y * width + left1;
+          blend_row((uint32_t*)dec->curr_frame_ + offset1,
+                    (uint32_t*)dec->prev_frame_disposed_ + offset1, width1);
+        }
+        if (width2 > 0) {
+          const size_t offset2 = canvas_y * width + left2;
+          blend_row((uint32_t*)dec->curr_frame_ + offset2,
+                    (uint32_t*)dec->prev_frame_disposed_ + offset2, width2);
+        }
+      }
+    }
+  }
+
+  // Update info of the previous frame and dispose it for the next iteration.
+  dec->prev_frame_timestamp_ = timestamp;
+  dec->prev_iter_ = iter;
+  dec->prev_frame_was_keyframe_ = is_key_frame;
+  CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height);
+  if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
+    ZeroFillFrameRect(dec->prev_frame_disposed_, width * NUM_CHANNELS,
+                      dec->prev_iter_.x_offset, dec->prev_iter_.y_offset,
+                      dec->prev_iter_.width, dec->prev_iter_.height);
+  }
+  ++dec->next_frame_;
+
+  // All OK, fill in the values.
+  *buf_ptr = dec->curr_frame_;
+  *timestamp_ptr = timestamp;
+  return 1;
+
+ Error:
+  WebPDemuxReleaseIterator(&iter);
+  return 0;
+}
+
+int WebPAnimDecoderHasMoreFrames(const WebPAnimDecoder* dec) {
+  if (dec == NULL) return 0;
+  return (dec->next_frame_ <= (int)dec->info_.frame_count);
+}
+
+void WebPAnimDecoderReset(WebPAnimDecoder* dec) {
+  if (dec != NULL) {
+    dec->prev_frame_timestamp_ = 0;
+    memset(&dec->prev_iter_, 0, sizeof(dec->prev_iter_));
+    dec->prev_frame_was_keyframe_ = 0;
+    dec->next_frame_ = 1;
+  }
+}
+
+const WebPDemuxer* WebPAnimDecoderGetDemuxer(const WebPAnimDecoder* dec) {
+  if (dec == NULL) return NULL;
+  return dec->demux_;
+}
+
+void WebPAnimDecoderDelete(WebPAnimDecoder* dec) {
+  if (dec != NULL) {
+    WebPDemuxDelete(dec->demux_);
+    WebPSafeFree(dec->curr_frame_);
+    WebPSafeFree(dec->prev_frame_disposed_);
+    WebPSafeFree(dec);
+  }
+}