From d77b877cc9a46645abc46fcb6b0ee8de777a1c23 Mon Sep 17 00:00:00 2001
From: Pascal Massimino <pascal.massimino@gmail.com>
Date: Wed, 1 Jun 2016 20:55:29 +0200
Subject: [PATCH] introduce a common signature for all image reader function

-> WebPImageReader

Introduce a variant of image-guessing function that returns a reader
directly: WebPGuessImageReader()

Change-Id: I5ddc53024fcf941e33d997b2be6aa1a963d939ab
---
 examples/cwebp.c     | 15 ++-------------
 examples/image_dec.c | 11 +++++++++++
 examples/image_dec.h | 10 ++++++++++
 examples/jpegdec.c   |  7 +++++--
 examples/jpegdec.h   |  5 ++++-
 5 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/examples/cwebp.c b/examples/cwebp.c
index 80924072..b538ae21 100644
--- a/examples/cwebp.c
+++ b/examples/cwebp.c
@@ -105,19 +105,8 @@ static int ReadPicture(const char* const filename, WebPPicture* const pic,
   if (!ok) goto End;
 
   if (pic->width == 0 || pic->height == 0) {
-    ok = 0;
-    if (data_size >= 12) {
-      const WebPInputFileFormat format = WebPGuessImageType(data, data_size);
-      if (format == WEBP_PNG_FORMAT) {
-        ok = ReadPNG(data, data_size, pic, keep_alpha, metadata);
-      } else if (format == WEBP_JPEG_FORMAT) {
-        ok = ReadJPEG(data, data_size, pic, metadata);
-      } else if (format == WEBP_TIFF_FORMAT) {
-        ok = ReadTIFF(data, data_size, pic, keep_alpha, metadata);
-      } else if (format == WEBP_WEBP_FORMAT) {
-        ok = ReadWebP(data, data_size, pic, keep_alpha, metadata);
-      }
-    }
+    WebPImageReader reader = WebPGuessImageReader(data, data_size);
+    ok = (reader != NULL) && reader(data, data_size, pic, keep_alpha, metadata);
   } else {
     // If image size is specified, infer it as YUV format.
     ok = ReadYUV(data, data_size, pic);
diff --git a/examples/image_dec.c b/examples/image_dec.c
index 0b3ea160..ac056440 100644
--- a/examples/image_dec.c
+++ b/examples/image_dec.c
@@ -33,3 +33,14 @@ WebPInputFileFormat WebPGuessImageType(const uint8_t* const data,
   }
   return format;
 }
+
+WebPImageReader WebPGuessImageReader(const uint8_t* const data,
+                                     size_t data_size) {
+  switch (WebPGuessImageType(data, data_size)) {
+    case WEBP_PNG_FORMAT: return ReadPNG;
+    case WEBP_JPEG_FORMAT: return ReadJPEG;
+    case WEBP_TIFF_FORMAT: return ReadTIFF;
+    case WEBP_WEBP_FORMAT: return ReadWebP;
+    default: return NULL;
+  }
+}
\ No newline at end of file
diff --git a/examples/image_dec.h b/examples/image_dec.h
index b12b3a85..de25e14f 100644
--- a/examples/image_dec.h
+++ b/examples/image_dec.h
@@ -44,6 +44,16 @@ typedef enum {
 WebPInputFileFormat WebPGuessImageType(const uint8_t* const data,
                                        size_t data_size);
 
+// Signature for common image-reading functions (ReadPNG, ReadJPEG, ...)
+typedef int (*WebPImageReader)(const uint8_t* const data, size_t data_size,
+                               struct WebPPicture* const pic,
+                               int keep_alpha, struct Metadata* const metadata);
+
+// This function is similar to WebPGuessImageType(), but returns a
+// suitable reader function. Or NULL if the image can't be guessed.
+WebPImageReader WebPGuessImageReader(const uint8_t* const data,
+                                     size_t data_size);
+
 #ifdef __cplusplus
 }    // extern "C"
 #endif
diff --git a/examples/jpegdec.c b/examples/jpegdec.c
index 244502da..94d95d4a 100644
--- a/examples/jpegdec.c
+++ b/examples/jpegdec.c
@@ -255,7 +255,8 @@ static void ContextSetup(volatile struct jpeg_decompress_struct* const cinfo,
 }
 
 int ReadJPEG(const uint8_t* const data, size_t data_size,
-             WebPPicture* const pic, Metadata* const metadata) {
+             WebPPicture* const pic, int keep_alpha,
+             Metadata* const metadata) {
   volatile int ok = 0;
   int stride, width, height;
   volatile struct jpeg_decompress_struct dinfo;
@@ -264,6 +265,7 @@ int ReadJPEG(const uint8_t* const data, size_t data_size,
   JSAMPROW buffer[1];
   JPEGReadContext ctx;
 
+  (void)keep_alpha;
   memset(&ctx, 0, sizeof(ctx));
   ctx.data = data;
   ctx.data_size = data_size;
@@ -333,11 +335,12 @@ int ReadJPEG(const uint8_t* const data, size_t data_size,
 }
 #else  // !WEBP_HAVE_JPEG
 int ReadJPEG(const uint8_t* const data, size_t data_size,
-             struct WebPPicture* const pic,
+             struct WebPPicture* const pic, int keep_alpha,
              struct Metadata* const metadata) {
   (void)data;
   (void)data_size;
   (void)pic;
+  (void)keep_alpha;
   (void)metadata;
   fprintf(stderr, "JPEG support not compiled. Please install the libjpeg "
           "development package before building.\n");
diff --git a/examples/jpegdec.h b/examples/jpegdec.h
index 68c042aa..9be463b1 100644
--- a/examples/jpegdec.h
+++ b/examples/jpegdec.h
@@ -25,8 +25,11 @@ struct WebPPicture;
 // Reads a JPEG from 'data', returning the decoded output in 'pic'.
 // The output is RGB or YUV depending on pic->use_argb value.
 // Returns true on success.
+// 'keep_alpha' has no effect, but is kept for coherence with other signatures
+// for image readers.
 int ReadJPEG(const uint8_t* const data, size_t data_size,
-             struct WebPPicture* const pic, struct Metadata* const metadata);
+             struct WebPPicture* const pic, int keep_alpha,
+             struct Metadata* const metadata);
 
 #ifdef __cplusplus
 }    // extern "C"