libwebp/src/webp.c

// Copyright 2010 Google Inc.
//
// This code is licensed under the same terms as WebM:
//  Software License Agreement:  http://www.webmproject.org/license/software/
//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
// Main decoding functions for WEBP images.
//
// Author: Skal (pascal.massimino@gmail.com)

#include <stdlib.h>
#include "vp8i.h"
#include "yuv.h"

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

//-----------------------------------------------------------------------------
// RIFF layout is:
//   0ffset  tag
//   0...3   "RIFF" 4-byte tag
//   4...7   size of image data (including metadata) starting at offset 8
//   8...11  "WEBP"   our form-type signature
//   12..15  "VP8 ": 4-bytes tags, describing the raw video format used
//   16..19  size of the raw VP8 image data, starting at offset 20
//   20....  the VP8 bytes
// There can be extra chunks after the "VP8 " chunk (ICMT, ICOP, ...)
// All 32-bits sizes are in little-endian order.
// Note: chunk data must be padded to multiple of 2 in size

static inline uint32_t get_le32(const uint8_t* const data) {
  return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
}

// If a RIFF container is detected, validate it and skip over it.
static int CheckRIFFHeader(const uint8_t** data_ptr, uint32_t *data_size_ptr) {
  uint32_t chunk_size = 0xffffffffu;
  if (*data_size_ptr >= 10 + 20 && !memcmp(*data_ptr, "RIFF", 4)) {
    if (memcmp(*data_ptr + 8, "WEBP", 4)) {
      return 0;  // wrong image file signature
    }
    const uint32_t riff_size = get_le32(*data_ptr + 4);
    if (memcmp(*data_ptr + 12, "VP8 ", 4)) {
      return 0;   // invalid compression format
    }
    chunk_size = get_le32(*data_ptr + 16);
    if ((chunk_size > riff_size + 8) || (chunk_size & 1)) {
      return 0;  // inconsistent size information.
    }
    // We have a IFF container. Skip it.
    *data_ptr += 20;
    *data_size_ptr -= 20;
  }
  return chunk_size;
}

//-----------------------------------------------------------------------------

typedef enum { MODE_RGB = 0, MODE_RGBA = 1,
               MODE_BGR = 2, MODE_BGRA = 3,
               MODE_YUV = 4 } CSP_MODE;

typedef struct {
  uint8_t* output;      // rgb(a) or luma
  uint8_t *u, *v;
  int stride;           // rgb(a) stride or luma stride
  int u_stride;
  int v_stride;
  CSP_MODE mode;
} Params;

static void CustomPut(const VP8Io* io) {
  Params *p = (Params*)io->opaque;
  const int mb_w = io->mb_w;
  const int mb_h = io->mb_h;
  if (p->mode == MODE_YUV) {
    uint8_t* const y_dst = p->output + io->mb_x + io->mb_y * p->stride;
    for (int j = 0; j < mb_h; ++j) {
      memcpy(y_dst + j * p->stride, io->y + j * io->y_stride, mb_w);
    }
    uint8_t* const u_dst = p->u + (io->mb_x / 2) + (io->mb_y / 2) * p->u_stride;
    uint8_t* const v_dst = p->v + (io->mb_x / 2) + (io->mb_y / 2) * p->v_stride;
    const int uv_w = (mb_w + 1) / 2;
    for (int j = 0; j < (mb_h + 1) / 2; ++j) {
      memcpy(u_dst + j * p->u_stride, io->u + j * io->uv_stride, uv_w);
      memcpy(v_dst + j * p->v_stride, io->v + j * io->uv_stride, uv_w);
    }
  } else {
    const int psize = (p->mode == MODE_RGB || p->mode == MODE_BGR) ? 3 : 4;
    uint8_t* dst = p->output + psize * io->mb_x + io->mb_y * p->stride;
    for (int j = 0; j < mb_h; ++j) {
      const uint8_t* y_src = io->y + j * io->y_stride;
      for (int i = 0; i < mb_w; ++i) {
        const int y = y_src[i];
        const int u = io->u[(j / 2) * io->uv_stride + (i / 2)];
        const int v = io->v[(j / 2) * io->uv_stride + (i / 2)];
        if (p->mode == MODE_RGB) {
          VP8YuvToRgb(y, u, v, dst + i * 3);
        } else if (p->mode == MODE_BGR) {
          VP8YuvToBgr(y, u, v, dst + i * 3);
        } else if (p->mode == MODE_RGBA) {
          VP8YuvToRgba(y, u, v, dst + i * 4);
        } else {
          VP8YuvToBgra(y, u, v, dst + i * 4);
        }
      }
      dst += p->stride;
    }
  }
}


//-----------------------------------------------------------------------------
// "Into" variants

static uint8_t* DecodeInto(CSP_MODE mode,
                           const uint8_t* data, uint32_t data_size,
                           Params* params, int output_size,
                           int output_u_size, int output_v_size) {
  VP8Decoder* dec = VP8New();
  if (dec == NULL) {
    return NULL;
  }

  VP8Io io;
  VP8InitIo(&io);
  io.data = data;
  io.data_size = data_size;

  params->mode = mode;
  io.opaque = params;
  io.put = CustomPut;

  if (!VP8GetHeaders(dec, &io)) {
    VP8Delete(dec);
    return NULL;
  }
  // check output buffers
  int ok = 1;
  ok &= (params->stride * io.height <= output_size);
  if (mode == MODE_RGB || mode == MODE_BGR) {
    ok &= (params->stride >= io.width * 3);
  } else if (mode == MODE_RGBA || mode == MODE_BGRA) {
    ok &= (params->stride >= io.width * 4);
  } else {
    ok &= (params->stride >= io.width);
    // some extra checks for U/V
    const int u_size = params->u_stride * ((io.height + 1) / 2);
    const int v_size = params->v_stride * ((io.height + 1) / 2);
    ok &= (params->u_stride >= (io.width + 1) / 2) &&
          (params->v_stride >= (io.width + 1) / 2);
    ok &= (u_size <= output_u_size && v_size <= output_v_size);
  }
  if (!ok) {
    VP8Delete(dec);
    return NULL;
  }

  if (mode != MODE_YUV) {
    VP8YUVInit();
  }

  ok = VP8Decode(dec, &io);
  VP8Delete(dec);
  return ok ? params->output : NULL;
}

uint8_t* WebPDecodeRGBInto(const uint8_t* data, uint32_t data_size,
                           uint8_t* output, int output_size,
                           int output_stride) {
  if (output == NULL) {
    return NULL;
  }
  Params params;
  params.output = output;
  params.stride = output_stride;
  return DecodeInto(MODE_RGB, data, data_size, &params, output_size, 0, 0);
}

uint8_t* WebPDecodeRGBAInto(const uint8_t* data, uint32_t data_size,
                            uint8_t* output, int output_size,
                            int output_stride) {
  if (output == NULL) {
    return NULL;
  }
  Params params;
  params.output = output;
  params.stride = output_stride;
  return DecodeInto(MODE_RGBA, data, data_size, &params, output_size, 0, 0);
}

uint8_t* WebPDecodeBGRInto(const uint8_t* data, uint32_t data_size,
                           uint8_t* output, int output_size,
                           int output_stride) {
  if (output == NULL) {
    return NULL;
  }
  Params params;
  params.output = output;
  params.stride = output_stride;
  return DecodeInto(MODE_BGR, data, data_size, &params, output_size, 0, 0);
}

uint8_t* WebPDecodeBGRAInto(const uint8_t* data, uint32_t data_size,
                            uint8_t* output, int output_size,
                            int output_stride) {
  if (output == NULL) {
    return NULL;
  }
  Params params;
  params.output = output;
  params.stride = output_stride;
  return DecodeInto(MODE_BGRA, data, data_size, &params, output_size, 0, 0);
}

uint8_t* WebPDecodeYUVInto(const uint8_t* data, uint32_t data_size,
                           uint8_t* luma, int luma_size, int luma_stride,
                           uint8_t* u, int u_size, int u_stride,
                           uint8_t* v, int v_size, int v_stride) {
  if (luma == NULL) {
    return NULL;
  }
  Params params;
  params.output = luma;
  params.stride = luma_stride;
  params.u = u;
  params.u_stride = u_stride;
  params.v = v;
  params.v_stride = v_stride;
  return DecodeInto(MODE_YUV, data, data_size, &params,
                    luma_size, u_size, v_size);
}

//-----------------------------------------------------------------------------

static uint8_t* Decode(CSP_MODE mode, const uint8_t* data, uint32_t data_size,
                       int* width, int* height, Params* params_out) {
  int w, h;
  if (!WebPGetInfo(data, data_size, &w, &h)) {
    return NULL;
  }
  if (width) *width = w;
  if (height) *height = h;

  // initialize output buffer, now that dimensions are known.
  int stride = (mode == MODE_RGB || mode == MODE_BGR) ? 3 * w
             : (mode == MODE_RGBA || mode == MODE_BGRA) ? 4 * w
             : w;
  const int size = stride * h;
  int uv_size = 0;
  int uv_stride = 0;
  if (mode == MODE_YUV) {
    uv_stride = (w + 1) / 2;
    uv_size = uv_stride * ((h + 1) / 2);
  }
  uint8_t* const output = (uint8_t*)malloc(size + 2 * uv_size);
  if (!output) {
    return NULL;
  }
  Params params = { 0 };
  params.output = output;
  params.stride = stride;
  if (mode == MODE_YUV) {
    params.u = output + size;
    params.u_stride = uv_stride;
    params.v = output + size + uv_size;
    params.v_stride = uv_stride;
  }
  if (params_out) *params_out = params;
  return DecodeInto(mode, data, data_size, &params, size, uv_size, uv_size);
}

uint8_t* WebPDecodeRGB(const uint8_t* data, uint32_t data_size,
                       int *width, int *height) {
  return Decode(MODE_RGB, data, data_size, width, height, NULL);
}

uint8_t* WebPDecodeRGBA(const uint8_t* data, uint32_t data_size,
                        int *width, int *height) {
  return Decode(MODE_RGBA, data, data_size, width, height, NULL);
}

uint8_t* WebPDecodeBGR(const uint8_t* data, uint32_t data_size,
                       int *width, int *height) {
  return Decode(MODE_BGR, data, data_size, width, height, NULL);
}

uint8_t* WebPDecodeBGRA(const uint8_t* data, uint32_t data_size,
                        int *width, int *height) {
  return Decode(MODE_BGRA, data, data_size, width, height, NULL);
}

uint8_t* WebPDecodeYUV(const uint8_t* data, uint32_t data_size,
                       int *width, int *height, uint8_t** u, uint8_t** v,
                       int *stride, int* uv_stride) {
  Params params;
  uint8_t* const out = Decode(MODE_YUV, data, data_size,
                              width, height, &params);

  if (out) {
    *u = params.u;
    *v = params.v;
    *stride = params.stride;
    *uv_stride = params.u_stride;
    assert(params.u_stride == params.v_stride);
  }
  return out;
}

//-----------------------------------------------------------------------------
// WebPGetInfo()

int WebPGetInfo(const uint8_t* data, uint32_t data_size,
                int *width, int *height) {
  const uint32_t chunk_size = CheckRIFFHeader(&data, &data_size);
  if (!chunk_size) {
    return 0;         // unsupported RIFF header
  }
  // Validate raw video data
  if (data_size < 10) {
    return 0;         // not enough data
  }
  // check signature
  if (data[3] != 0x9d || data[4] != 0x01 || data[5] != 0x2a) {
    return 0;         // Wrong signature.
  }
  const uint32_t bits = data[0] | (data[1] << 8) | (data[2] << 16);
  const int key_frame = !(bits & 1);
  if (!key_frame) {   // Not a keyframe.
    return 0;
  }
  const int profile = (bits >> 1) & 7;
  const int show_frame  = (bits >> 4) & 1;
  const uint32_t partition_length = (bits >> 5);
  if (profile > 3) {
    return 0;         // unknown profile
  }
  if (!show_frame) {
    return 0;         // first frame is invisible!
  }
  if (partition_length >= chunk_size) {
    return 0;         // inconsistent size information.
  }

  const int w = ((data[7] << 8) | data[6]) & 0x3fff;
  const int h = ((data[9] << 8) | data[8]) & 0x3fff;
  if (width) {
    *width = w;
  }
  if (height) {
    *height = h;
  }

  return 1;
}

#if defined(__cplusplus) || defined(c_plusplus)
}    // extern "C"
#endif