AnimEncoder: Add a GetError() method.

We now get error string instead of printing it.
The verbose option is now only used to print info and warnings.

Change-Id: I985c5acd427a9d1973068e7b7a8af5dd0d6d2585

examples/gif2webp.c

@@ -314,7 +314,12 @@ int main(int argc, const char *argv[]) {
           // Initialize encoder.
           enc = WebPAnimEncoderNew(curr_canvas.width, curr_canvas.height,
                                    &enc_options);
-          if (enc == NULL) goto End;
+          if (enc == NULL) {
+            fprintf(stderr,
+                    "Error! Could not create encoder object. Possibly due to "
+                    "a memory error.\n");
+            goto End;
+          }
           is_first_frame = 0;
         }
 
@@ -332,8 +337,7 @@ int main(int argc, const char *argv[]) {
         GIFBlendFrames(&frame, &gif_rect, &curr_canvas);
 
         if (!WebPAnimEncoderAdd(enc, &curr_canvas, frame_timestamp, &config)) {
-          fprintf(stderr, "Error! Cannot encode frame as WebP\n");
+          fprintf(stderr, "%s\n", WebPAnimEncoderGetError(enc));
-          fprintf(stderr, "Error code: %d\n", curr_canvas.error_code);
         }
 
         // Update canvases.
@@ -431,11 +435,11 @@ int main(int argc, const char *argv[]) {
   // Last NULL frame.
   if (!WebPAnimEncoderAdd(enc, NULL, frame_timestamp, NULL)) {
     fprintf(stderr, "Error flushing WebP muxer.\n");
+    fprintf(stderr, "%s\n", WebPAnimEncoderGetError(enc));
   }
 
   if (!WebPAnimEncoderAssemble(enc, &webp_data)) {
-    // TODO(urvang): Print actual error code.
+    fprintf(stderr, "%s\n", WebPAnimEncoderGetError(enc));
-    fprintf(stderr, "ERROR assembling the WebP file.\n");
     goto End;
   }
 

src/mux/anim_encode.c

@@ -20,6 +20,12 @@
 #include "../webp/format_constants.h"
 #include "../webp/mux.h"
 
+#if defined(_MSC_VER) && _MSC_VER < 1900
+#define snprintf _snprintf
+#endif
+
+#define ERROR_STR_MAX_LENGTH 100
+
 //------------------------------------------------------------------------------
 // Internal structs.
 
@@ -86,6 +92,7 @@ struct WebPAnimEncoder {
                             // different from 'in_frame_count_' due to merging.
 
   WebPMux* mux_;        // Muxer to assemble the WebP bitstream.
+  char error_str_[ERROR_STR_MAX_LENGTH];  // Error string. Empty if no error.
 };
 
 // -----------------------------------------------------------------------------
@@ -166,7 +173,6 @@ static void DefaultEncoderOptions(WebPAnimEncoderOptions* const enc_options) {
   enc_options->minimize_size = 0;
   DisableKeyframes(enc_options);
   enc_options->allow_mixed = 0;
-  enc_options->verbose = 0;
 }
 
 int WebPAnimEncoderOptionsInitInternal(WebPAnimEncoderOptions* enc_options,
@@ -203,6 +209,24 @@ static void WebPUtilClearPic(WebPPicture* const picture,
   }
 }
 
+static void MarkNoError(WebPAnimEncoder* const enc) {
+  enc->error_str_[0] = '\0';  // Empty string.
+}
+
+static void MarkError(WebPAnimEncoder* const enc, const char* str) {
+  if (snprintf(enc->error_str_, ERROR_STR_MAX_LENGTH, "%s.", str) < 0) {
+    assert(0);  // FIX ME!
+  }
+}
+
+static void MarkError2(WebPAnimEncoder* const enc,
+                       const char* str, int error_code) {
+  if (snprintf(enc->error_str_, ERROR_STR_MAX_LENGTH, "%s: %d.", str,
+               error_code) < 0) {
+    assert(0);  // FIX ME!
+  }
+}
+
 WebPAnimEncoder* WebPAnimEncoderNewInternal(
     int width, int height, const WebPAnimEncoderOptions* enc_options,
     int abi_version) {
@@ -221,6 +245,7 @@ WebPAnimEncoder* WebPAnimEncoderNewInternal(
   // sanity inits, so we can call WebPAnimEncoderDelete():
   enc->encoded_frames_ = NULL;
   enc->mux_ = NULL;
+  MarkNoError(enc);
 
   // Dimensions and options.
   *(int*)&enc->canvas_width_ = width;
@@ -236,7 +261,7 @@ WebPAnimEncoder* WebPAnimEncoderNewInternal(
   if (!WebPPictureInit(&enc->curr_canvas_copy_) ||
       !WebPPictureInit(&enc->prev_canvas_) ||
       !WebPPictureInit(&enc->prev_canvas_disposed_)) {
-    return NULL;
+    goto Err;
   }
   enc->curr_canvas_copy_.width = width;
   enc->curr_canvas_copy_.height = height;
@@ -287,7 +312,7 @@ static void FrameRelease(EncodedFrame* const encoded_frame) {
 }
 
 void WebPAnimEncoderDelete(WebPAnimEncoder* enc) {
-  if (enc != NULL) {;
+  if (enc != NULL) {
     WebPPictureFree(&enc->curr_canvas_copy_);
     WebPPictureFree(&enc->prev_canvas_);
     WebPPictureFree(&enc->prev_canvas_disposed_);
@@ -1106,9 +1131,8 @@ static int CacheFrame(WebPAnimEncoder* const enc,
     // We reset some counters, as the frame addition failed/was skipped.
     --enc->count_;
     if (!enc->is_first_frame_) --enc->count_since_key_frame_;
-    if (!ok && enc->options_.verbose) {
+    if (!ok) {
-      fprintf(stderr, "ERROR adding frame. WebPEncodingError: %d.\n",
+      MarkError2(enc, "ERROR adding frame. WebPEncodingError", error_code);
-              error_code);
     }
   }
   enc->curr_canvas_->error_code = error_code;   // report error_code
@@ -1125,13 +1149,11 @@ static int FlushFrames(WebPAnimEncoder* const enc) {
     assert(enc->mux_ != NULL);
     err = WebPMuxPushFrame(enc->mux_, info, 1);
     if (err != WEBP_MUX_OK) {
-      if (enc->options_.verbose) {
+      MarkError2(enc, "ERROR adding frame. WebPMuxError", err);
-        fprintf(stderr, "ERROR adding frame. WebPMuxError: %d.\n", err);
-      }
       return 0;
     }
     if (enc->options_.verbose) {
-      fprintf(stderr, "Added frame. offset:%d,%d dispose:%d blend:%d\n",
+      fprintf(stderr, "INFO: Added frame. offset:%d,%d dispose:%d blend:%d\n",
               info->x_offset, info->y_offset, info->dispose_method,
               info->blend_method);
     }
@@ -1165,6 +1187,7 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
   if (enc == NULL) {
     return 0;
   }
+  MarkNoError(enc);
 
   if (!enc->is_first_frame_) {
     // Make sure timestamps are non-decreasing (integer wrap-around is OK).
@@ -1174,10 +1197,7 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
       if (frame != NULL) {
         frame->error_code = VP8_ENC_ERROR_INVALID_CONFIGURATION;
       }
-      if (enc->options_.verbose) {
+      MarkError(enc, "ERROR adding frame: timestamps must be non-decreasing");
-        fprintf(stderr,
-                "ERROR adding frame: timestamps must be non-decreasing.\n");
-      }
       return 0;
     }
     if (!IncreasePreviousDuration(enc, (int)prev_frame_duration)) {
@@ -1196,9 +1216,7 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
   if (frame->width != enc->canvas_width_ ||
       frame->height != enc->canvas_height_) {
     frame->error_code = VP8_ENC_ERROR_INVALID_CONFIGURATION;
-    if (enc->options_.verbose) {
+    MarkError(enc, "ERROR adding frame: Invalid frame dimensions");
-      fprintf(stderr, "ERROR adding frame: Invalid frame dimensions.\n");
-    }
     return 0;
   }
 
@@ -1208,7 +1226,7 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
               "this incurs a small loss.\n");
     }
     if (!WebPPictureYUVAToARGB(frame)) {
-      fprintf(stderr, "ERROR converting frame from YUV(A) to ARGB\n");
+      MarkError(enc, "ERROR converting frame from YUV(A) to ARGB");
       return 0;
     }
   }
@@ -1348,17 +1366,15 @@ int WebPAnimEncoderAssemble(WebPAnimEncoder* enc, WebPData* webp_data) {
   if (enc == NULL) {
     return 0;
   }
+  MarkNoError(enc);
+
   if (webp_data == NULL) {
-    if (enc->options_.verbose) {
+    MarkError(enc, "ERROR assembling: NULL input");
-      fprintf(stderr, "ERROR assembling: NULL input\n");
-    }
     return 0;
   }
 
   if (enc->in_frame_count_ == 0) {
-    if (enc->options_.verbose) {
+    MarkError(enc, "ERROR: No frames to assemble");
-      fprintf(stderr, "ERROR: No frames to assemble\n");
-    }
     return 0;
   }
 
@@ -1393,14 +1409,16 @@ int WebPAnimEncoderAssemble(WebPAnimEncoder* enc, WebPData* webp_data) {
     err = OptimizeSingleFrame(enc, webp_data);
     if (err != WEBP_MUX_OK) goto Err;
   }
-
   return 1;
 
  Err:
-  if (enc->options_.verbose) {
+  MarkError2(enc, "ERROR assembling WebP", err);
-    fprintf(stderr, "ERROR assembling WebP: %d\n", err);
-  }
   return 0;
 }
 
+const char* WebPAnimEncoderGetError(WebPAnimEncoder* enc) {
+  if (enc == NULL) return NULL;
+  return enc->error_str_;
+}
+
 // -----------------------------------------------------------------------------

src/webp/mux.h

@@ -21,7 +21,7 @@
 extern "C" {
 #endif
 
-#define WEBP_MUX_ABI_VERSION 0x0105        // MAJOR(8b) + MINOR(8b)
+#define WEBP_MUX_ABI_VERSION 0x0106        // MAJOR(8b) + MINOR(8b)
 
 //------------------------------------------------------------------------------
 // Mux API
@@ -436,10 +436,8 @@ struct WebPAnimEncoderOptions {
                         // then all frames will be key-frames.
   int allow_mixed;      // If true, use mixed compression mode; may choose
                         // either lossy and lossless for each frame.
+  int verbose;          // If true, print info and warning messages to stderr.
 
-  // TODO(urvang): Instead of printing errors to STDERR, we should have an error
-  // string attached to the encoder.
-  int verbose;          // If true, print encoding info.
   uint32_t padding[4];  // Padding for later use.
 };
 
@@ -508,10 +506,20 @@ WEBP_EXTERN(int) WebPAnimEncoderAdd(
 WEBP_EXTERN(int) WebPAnimEncoderAssemble(WebPAnimEncoder* enc,
                                          WebPData* webp_data);
 
+// Get error string corresponding to the most recent call using 'enc'. The
+// returned string is owned by 'enc' and is valid only until the next call to
+// WebPAnimEncoderAdd() or WebPAnimEncoderAssemble() or WebPAnimEncoderDelete().
+// Parameters:
+//   enc - (in/out) object from which the error string is to be fetched.
+// Returns:
+//   NULL if 'enc' is NULL. Otherwise, returns the error string if the last call
+//   to 'enc' had an error, or an empty string if the last call was a success.
+WEBP_EXTERN(const char*) WebPAnimEncoderGetError(WebPAnimEncoder* enc);
+
 // Deletes the WebPAnimEncoder object.
 // Parameters:
-//   anim_enc - (in/out) object to be deleted
+//   enc - (in/out) object to be deleted
-WEBP_EXTERN(void) WebPAnimEncoderDelete(WebPAnimEncoder* anim_enc);
+WEBP_EXTERN(void) WebPAnimEncoderDelete(WebPAnimEncoder* enc);
 
 //------------------------------------------------------------------------------