int WebPEncode()

in Extended/libwebp/src/enc/webp_enc.c [328:410]
66 lines of code
30 McCabe index (conditional complexity)

int WebPEncode(const WebPConfig* config, WebPPicture* pic) {
  int ok = 0;
  if (pic == NULL) return 0;

  WebPEncodingSetError(pic, VP8_ENC_OK);  // all ok so far
  if (config == NULL) {  // bad params
    return WebPEncodingSetError(pic, VP8_ENC_ERROR_NULL_PARAMETER);
  }
  if (!WebPValidateConfig(config)) {
    return WebPEncodingSetError(pic, VP8_ENC_ERROR_INVALID_CONFIGURATION);
  }
  if (pic->width <= 0 || pic->height <= 0) {
    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_DIMENSION);
  }
  if (pic->width > WEBP_MAX_DIMENSION || pic->height > WEBP_MAX_DIMENSION) {
    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_DIMENSION);
  }

  if (pic->stats != NULL) memset(pic->stats, 0, sizeof(*pic->stats));

  if (!config->lossless) {
    VP8Encoder* enc = NULL;

    if (pic->use_argb || pic->y == NULL || pic->u == NULL || pic->v == NULL) {
      // Make sure we have YUVA samples.
      if (config->use_sharp_yuv || (config->preprocessing & 4)) {
        if (!WebPPictureSharpARGBToYUVA(pic)) {
          return 0;
        }
      } else {
        float dithering = 0.f;
        if (config->preprocessing & 2) {
          const float x = config->quality / 100.f;
          const float x2 = x * x;
          // slowly decreasing from max dithering at low quality (q->0)
          // to 0.5 dithering amplitude at high quality (q->100)
          dithering = 1.0f + (0.5f - 1.0f) * x2 * x2;
        }
        if (!WebPPictureARGBToYUVADithered(pic, WEBP_YUV420, dithering)) {
          return 0;
        }
      }
    }

    if (!config->exact) {
      WebPCleanupTransparentArea(pic);
    }

    enc = InitVP8Encoder(config, pic);
    if (enc == NULL) return 0;  // pic->error is already set.
    // Note: each of the tasks below account for 20% in the progress report.
    ok = VP8EncAnalyze(enc);

    // Analysis is done, proceed to actual coding.
    ok = ok && VP8EncStartAlpha(enc);   // possibly done in parallel
    if (!enc->use_tokens_) {
      ok = ok && VP8EncLoop(enc);
    } else {
      ok = ok && VP8EncTokenLoop(enc);
    }
    ok = ok && VP8EncFinishAlpha(enc);

    ok = ok && VP8EncWrite(enc);
    StoreStats(enc);
    if (!ok) {
      VP8EncFreeBitWriters(enc);
    }
    ok &= DeleteVP8Encoder(enc);  // must always be called, even if !ok
  } else {
    // Make sure we have ARGB samples.
    if (pic->argb == NULL && !WebPPictureYUVAToARGB(pic)) {
      return 0;
    }

    if (!config->exact) {
      WebPCleanupTransparentAreaLossless(pic);
    }

    ok = VP8LEncodeImage(config, pic);  // Sets pic->error in case of problem.
  }

  return ok;
}