Add error reporting from encoding failures.

picture->error_code can be looked up for finer error diagnose.
Added readable error messages to cwebp too.

Should close bug #75 (http://code.google.com/p/webp/issues/detail?id=75)

Change-Id: I8889d06642d90702f698cd5c27441a058ddb3636

examples/cwebp.c

@@ -637,6 +637,21 @@ static void HelpLong(void) {
   printf("\n");
 }
 
+//-----------------------------------------------------------------------------
+// Error messages
+
+static const char* const kErrorMessages[] = {
+  "OK",
+  "OUT_OF_MEMORY: Out of memory allocating objects",
+  "BITSTREAM_OUT_OF_MEMORY: Out of memory re-allocating byte buffer",
+  "NULL_PARAMETER: NULL parameter passed to function",
+  "INVALID_CONFIGURATION: configuration is invalid",
+  "BAD_DIMENSION: Bad picture dimension",
+  "PARTITION0_OVERFLOW: Partition #0 is too big to fit 512k",
+  "PARTITION_OVERFLOW: Partition is too big to fir 16M",
+  "BAD_WRITE: Picture writer returned an error"
+};
+
 //-----------------------------------------------------------------------------
 
 int main(int argc, const char *argv[]) {
@@ -833,6 +848,8 @@ int main(int argc, const char *argv[]) {
   }
   if (!WebPEncode(&config, &picture)) {
     fprintf(stderr, "Error! Cannot encode picture as WebP\n");
+    fprintf(stderr, "Error code: %d (%s)\n",
+            picture.error_code, kErrorMessages[picture.error_code]);
     goto Error;
   }
   if (verbose) {

src/enc/syntax.c

@@ -39,21 +39,22 @@ static void PutLE32(uint8_t* const data, uint32_t val) {
 }
 
 static int PutHeader(int profile, size_t size0, size_t total_size,
-                     const WebPPicture* const pic) {
+                     WebPPicture* const pic) {
   uint8_t buf[KHEADER_SIZE];
   uint8_t RIFF[KRIFF_SIZE] = {
     'R', 'I', 'F', 'F', 0, 0, 0, 0, 'W', 'E', 'B', 'P', 'V', 'P', '8', ' '
   };
   uint32_t bits;
 
-  if (size0 >= MAX_PARTITION0_SIZE) {
+  if (size0 >= MAX_PARTITION0_SIZE) {  // partition #0 is too big to fit
-    return 0;   // partition #0 is too big to fit
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_PARTITION0_OVERFLOW);
   }
 
   PutLE32(RIFF + 4, total_size + KSIZE_OFFSET);
   PutLE32(RIFF + 16, total_size);
-  if (!pic->writer(RIFF, sizeof(RIFF), pic))
+  if (!pic->writer(RIFF, sizeof(RIFF), pic)) {
-    return 0;
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_WRITE);
+  }
 
   bits = 0               // keyframe (1b)
        | (profile << 1)  // profile (3b)
@@ -138,13 +139,13 @@ static void PutQuant(VP8BitWriter* const bw,
 
 // Partition sizes
 static int EmitPartitionsSize(const VP8Encoder* const enc,
-                              const WebPPicture* const pic) {
+                              WebPPicture* const pic) {
   uint8_t buf[3 * (MAX_NUM_PARTITIONS - 1)];
   int p;
   for (p = 0; p < enc->num_parts_ - 1; ++p) {
     const size_t part_size = VP8BitWriterSize(enc->parts_ + p);
     if (part_size >= MAX_PARTITION_SIZE) {
-      return 0;     // partition is too big to fit
+      return WebPEncodingSetError(pic, VP8_ENC_ERROR_PARTITION_OVERFLOW);
     }
     buf[3 * p + 0] = (part_size >>  0) & 0xff;
     buf[3 * p + 1] = (part_size >>  8) & 0xff;
@@ -167,6 +168,7 @@ static int WriteExtensions(VP8Encoder* const enc) {
   const int kTrailerSize = 8;
   uint8_t buffer[kTrailerSize];
   VP8BitWriter* const bw = &enc->bw_;
+  WebPPicture* const pic = enc->pic_;
 
   // Layer (bytes 0..3)
   PutLE24(buffer + 0, enc->layer_data_size_);
@@ -176,7 +178,7 @@ static int WriteExtensions(VP8Encoder* const enc) {
     // append layer data to last partition
     if (!VP8BitWriterAppend(&enc->parts_[enc->num_parts_ - 1],
                             enc->layer_data_, enc->layer_data_size_)) {
-      return 0;
+      return WebPEncodingSetError(pic, VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY);
     }
   }
   // Alpha (bytes 4..6)
@@ -184,17 +186,18 @@ static int WriteExtensions(VP8Encoder* const enc) {
   if (enc->alpha_data_size_ > 0) {
     assert(enc->has_alpha_);
     if (!VP8BitWriterAppend(bw, enc->alpha_data_, enc->alpha_data_size_)) {
-      return 0;
+      return WebPEncodingSetError(pic, VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY);
     }
   }
 
   buffer[kTrailerSize - 1] = 0x01;  // marker
   if (!VP8BitWriterAppend(bw, buffer, kTrailerSize)) {
-    return 0;
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY);
   }
   return 1;
 }
-#endif
+
+#endif    /* WEBP_EXPERIMENTAL_FEATURES */
 
 //-----------------------------------------------------------------------------
 

src/enc/vp8enci.h

@@ -417,6 +417,9 @@ int VP8GetCostUV(VP8EncIterator* const it, const VP8ModeScore* const rd);
 int VP8EncLoop(VP8Encoder* const enc);
 int VP8StatLoop(VP8Encoder* const enc);
 
+  // in webpenc.c
+// Assign an error code to a picture. Return false for convenience.
+int WebPEncodingSetError(WebPPicture* const pic, WebPEncodingError error);
   // in analysis.c
 // Compute susceptibility based on DCT-coeff histograms:
 // the higher, the "easier" the macroblock is to compress.

src/enc/webpenc.c

@@ -9,6 +9,7 @@
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
+#include <assert.h>
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
@@ -53,6 +54,7 @@ int WebPPictureInitInternal(WebPPicture* const picture, int version) {
   if (picture) {
     memset(picture, 0, sizeof(*picture));
     picture->writer = DummyWriter;
+    WebPEncodingSetError(picture, VP8_ENC_OK);
   }
   return 1;
 }
@@ -194,7 +196,10 @@ static VP8Encoder* InitEncoder(const WebPConfig* const config,
   printf("===================================\n");
 #endif
   mem = (uint8_t*)malloc(size);
-  if (mem == NULL) return NULL;
+  if (mem == NULL) {
+    WebPEncodingSetError(picture, VP8_ENC_ERROR_OUT_OF_MEMORY);
+    return NULL;
+  }
   enc = (VP8Encoder*)mem;
   mem = (uint8_t*)DO_ALIGN(mem + sizeof(*enc));
   memset(enc, 0, sizeof(*enc));
@@ -296,25 +301,35 @@ static void StoreStats(VP8Encoder* const enc) {
   }
 }
 
+int WebPEncodingSetError(WebPPicture* const pic, WebPEncodingError error) {
+  assert((int)error <= VP8_ENC_ERROR_BAD_WRITE);
+  assert((int)error >= VP8_ENC_OK);
+  pic->error_code = error;
+  return 0;
+}
+
 //-----------------------------------------------------------------------------
 
 int WebPEncode(const WebPConfig* const config, WebPPicture* const pic) {
   VP8Encoder* enc;
   int ok;
 
-  if (config == NULL || pic == NULL)
+  if (pic == NULL)
-    return 0;   // bad params
+    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 0;   // invalid config.
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_INVALID_CONFIGURATION);
   if (pic->width <= 0 || pic->height <= 0)
-    return 0;   // invalid parameters
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_DIMENSION);
   if (pic->y == NULL || pic->u == NULL || pic->v == NULL)
-    return 0;   // invalid parameters
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_NULL_PARAMETER);
   if (pic->width >= MAX_DIMENSION || pic->height >= MAX_DIMENSION)
-    return 0;   // image is too big
+    return WebPEncodingSetError(pic, VP8_ENC_ERROR_BAD_DIMENSION);
 
   enc = InitEncoder(config, pic);
-  if (enc == NULL) return 0;
+  if (enc == NULL) return 0;  // pic->error is already set.
   ok = VP8EncAnalyze(enc)
     && VP8StatLoop(enc)
     && VP8EncLoop(enc)
@@ -325,6 +340,7 @@ int WebPEncode(const WebPConfig* const config, WebPPicture* const pic) {
     && VP8EncWrite(enc);
   StoreStats(enc);
   DeleteEncoder(enc);
+
   return ok;
 }
 

src/webp/encode.h

@@ -146,6 +146,19 @@ typedef enum {
   WEBP_CSP_ALPHA_BIT = 4   // bit that is set if alpha is present
 } WebPEncCSP;
 
+// Encoding error conditions.
+typedef enum {
+  VP8_ENC_OK = 0,
+  VP8_ENC_ERROR_OUT_OF_MEMORY,            // memory error allocating objects
+  VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY,  // memory error while flushing bits
+  VP8_ENC_ERROR_NULL_PARAMETER,           // a pointer parameter is NULL
+  VP8_ENC_ERROR_INVALID_CONFIGURATION,    // configuration is invalid
+  VP8_ENC_ERROR_BAD_DIMENSION,            // picture has invalid width/height
+  VP8_ENC_ERROR_PARTITION0_OVERFLOW,      // partition is too bigger than 16M
+  VP8_ENC_ERROR_PARTITION_OVERFLOW,       // partition is too bigger than 512k
+  VP8_ENC_ERROR_BAD_WRITE,                // error while flushing bytes
+} WebPEncodingError;
+
 struct WebPPicture {
   // input
   WebPEncCSP colorspace;     // colorspace: should be YUV420 for now (=Y'CbCr).
@@ -175,6 +188,8 @@ struct WebPPicture {
   // original samples (for non-YUV420 modes)
   uint8_t *u0, *v0;
   int uv0_stride;
+
+  WebPEncodingError error_code;   // error code in case of problem.
 };
 
 // Internal, version-checked, entry point
@@ -238,6 +253,7 @@ int WebPPictureImportBGRA(WebPPicture* const picture,
 // 'picture' must be less than 16384x16384 in dimension, and the 'config' object
 // must be a valid one.
 // Returns false in case of error, true otherwise.
+// In case of error, picture->error_code is updated accordingly.
 int WebPEncode(const WebPConfig* const config, WebPPicture* const picture);
 
 //-----------------------------------------------------------------------------