Backed-out PNG8 patch (no time to look at why

[wxWidgets.git] / src / common / imagjpeg.cpp

diff --git a/src/common/imagjpeg.cpp b/src/common/imagjpeg.cpp
index 245f8d911c5b944edb48d88f0a1748c1907aae22..d7cd54a73c863488a946f48b10c11d27b79d06cc 100644 (file)
--- a/src/common/imagjpeg.cpp
+++ b/src/common/imagjpeg.cpp
@@ -7,10 +7,9 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 

-/*
-   We don't put pragma implement in this file because it is already present in
-   src/common/image.cpp
-*/
+#if defined(__GNUG__) && !defined(NO_GCC_PRAGMA)
+#pragma implementation "imagjpeg.h"
+#endif

 
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"


@@ -21,17 +20,32 @@
 
 #include "wx/defs.h"
 
 
 #include "wx/defs.h"
 

-#if wxUSE_LIBJPEG
+#if wxUSE_IMAGE && wxUSE_LIBJPEG

 
 

-#include "wx/image.h"
+#include "wx/imagjpeg.h"

 #include "wx/bitmap.h"
 #include "wx/debug.h"
 #include "wx/log.h"
 #include "wx/app.h"
 #include "wx/bitmap.h"
 #include "wx/debug.h"
 #include "wx/log.h"
 #include "wx/app.h"

+
+// NB: Some compilers define boolean type in Windows headers
+//     (e.g. Watcom C++, but not Open Watcom).
+//     This causes a conflict with jmorecfg.h header from libjpeg, so we have
+//     to make sure libjpeg won't try to define boolean itself. This is done by
+//     defining HAVE_BOOLEAN.
+#if defined(__WXMSW__) && (defined(__MWERKS__) || defined(__DIGITALMARS__) || (defined(__WATCOMC__) && __WATCOMC__ < 1200))
+    #define HAVE_BOOLEAN
+    #include "wx/msw/wrapwin.h"
+#endif
+

 extern "C"
 {
 extern "C"
 {

+    #if defined(__WXMSW__)
+        #define XMD_H
+    #endif

     #include "jpeglib.h"
 }
     #include "jpeglib.h"
 }

+

 #include "wx/filefn.h"
 #include "wx/wfstream.h"
 #include "wx/intl.h"
 #include "wx/filefn.h"
 #include "wx/wfstream.h"
 #include "wx/intl.h"


@@ -43,13 +57,25 @@ extern "C"
 #include <setjmp.h>
 
 #ifdef __SALFORDC__
 #include <setjmp.h>
 
 #ifdef __SALFORDC__

-#ifdef FAR

 #undef FAR
 #endif
 #undef FAR
 #endif

-#endif

 
 

-#ifdef __WXMSW__
-#include <windows.h>
+// ----------------------------------------------------------------------------
+// types
+// ----------------------------------------------------------------------------
+
+// the standard definition of METHODDEF(type) from jmorecfg.h is "static type"
+// which means that we can't declare the method functions as extern "C" - the
+// compiler (rightfully) complains about the multiple storage classes in
+// declaration
+//
+// so we only add extern "C" when using our own, modified, jmorecfg.h - and use
+// whatever we have in the system headers if this is what we use hoping that it
+// should be ok (can't do anything else)
+#ifdef JPEG_METHOD_LINKAGE
+    #define CPP_METHODDEF(type) extern "C" METHODDEF(type)
+#else // not using our jmorecfg.h header
+    #define CPP_METHODDEF(type) METHODDEF(type)

 #endif
 
 //-----------------------------------------------------------------------------
 #endif
 
 //-----------------------------------------------------------------------------


@@ -62,81 +88,82 @@ IMPLEMENT_DYNAMIC_CLASS(wxJPEGHandler,wxImageHandler)
 
 //------------- JPEG Data Source Manager
 
 
 //------------- JPEG Data Source Manager
 

+#define JPEG_IO_BUFFER_SIZE   2048
+

 typedef struct {
     struct jpeg_source_mgr pub;   /* public fields */
 
     JOCTET* buffer;               /* start of buffer */
 typedef struct {
     struct jpeg_source_mgr pub;   /* public fields */
 
     JOCTET* buffer;               /* start of buffer */

-} my_source_mgr;
+    wxInputStream *stream;
+} wx_source_mgr;

 
 

-typedef my_source_mgr * my_src_ptr;
+typedef wx_source_mgr * wx_src_ptr;

 
 

-METHODDEF(void) my_init_source ( j_decompress_ptr WXUNUSED(cinfo) )
+CPP_METHODDEF(void) wx_init_source ( j_decompress_ptr WXUNUSED(cinfo) )

 {
 }
 
 {
 }
 

-METHODDEF(boolean) my_fill_input_buffer ( j_decompress_ptr WXUNUSED(cinfo) )
+CPP_METHODDEF(boolean) wx_fill_input_buffer ( j_decompress_ptr cinfo )

 {
 {

-    return TRUE;
-}
+    wx_src_ptr src = (wx_src_ptr) cinfo->src;

 
 

-METHODDEF(void) my_skip_input_data ( j_decompress_ptr cinfo, long num_bytes )
-{
-    my_src_ptr src = (my_src_ptr) cinfo->src;
+    src->pub.next_input_byte = src->buffer;
+    src->pub.bytes_in_buffer = src->stream->Read(src->buffer, JPEG_IO_BUFFER_SIZE).LastRead();

 
 

-    src->pub.next_input_byte += (size_t) num_bytes;
-    src->pub.bytes_in_buffer -= (size_t) num_bytes;
+    if (src->pub.bytes_in_buffer == 0) // check for end-of-stream
+    {
+        // Insert a fake EOI marker
+        src->buffer[0] = 0xFF;
+        src->buffer[1] = JPEG_EOI;
+        src->pub.bytes_in_buffer = 2;
+    }
+    return TRUE;

 }
 
 }
 

-METHODDEF(void) my_term_source ( j_decompress_ptr cinfo )
+CPP_METHODDEF(void) wx_skip_input_data ( j_decompress_ptr cinfo, long num_bytes )

 {
 {

-    my_src_ptr src = (my_src_ptr) cinfo->src;
-
-    free (src->buffer);
+    if (num_bytes > 0)
+    {
+        wx_src_ptr src = (wx_src_ptr) cinfo->src;
+
+        while (num_bytes > (long)src->pub.bytes_in_buffer)
+        {
+            num_bytes -= (long) src->pub.bytes_in_buffer;
+            src->pub.fill_input_buffer(cinfo);
+        }
+        src->pub.next_input_byte += (size_t) num_bytes;
+        src->pub.bytes_in_buffer -= (size_t) num_bytes;
+    }

 }
 
 }
 

-void jpeg_wxio_src( j_decompress_ptr cinfo, wxInputStream& infile )
+CPP_METHODDEF(void) wx_term_source ( j_decompress_ptr cinfo )

 {
 {

-    my_src_ptr src;
+    wx_src_ptr src = (wx_src_ptr) cinfo->src;

 
 

-    if (cinfo->src == NULL) {    /* first time for this JPEG object? */
-        cinfo->src = (struct jpeg_source_mgr *)
-            (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
-            sizeof(my_source_mgr));
-        src = (my_src_ptr) cinfo->src;
-    }
-    src = (my_src_ptr) cinfo->src;
-    src->pub.bytes_in_buffer = infile.GetSize(); /* forces fill_input_buffer on first read */
-    src->buffer = (JOCTET *) malloc (infile.GetSize());
-    src->pub.next_input_byte = src->buffer; /* until buffer loaded */
-    infile.Read(src->buffer, infile.GetSize());
-
-    src->pub.init_source = my_init_source;
-    src->pub.fill_input_buffer = my_fill_input_buffer;
-    src->pub.skip_input_data = my_skip_input_data;
-    src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
-    src->pub.term_source = my_term_source;
+    if (src->pub.bytes_in_buffer > 0)
+        src->stream->SeekI(-(long)src->pub.bytes_in_buffer, wxFromCurrent);
+    delete[] src->buffer;

 }
 
 
 // JPEG error manager:
 
 }
 
 
 // JPEG error manager:
 

-struct my_error_mgr {
+struct wx_error_mgr {

   struct jpeg_error_mgr pub;    /* "public" fields */
 
   jmp_buf setjmp_buffer;    /* for return to caller */
 };
 
   struct jpeg_error_mgr pub;    /* "public" fields */
 
   jmp_buf setjmp_buffer;    /* for return to caller */
 };
 

-typedef struct my_error_mgr * my_error_ptr;
+typedef struct wx_error_mgr * wx_error_ptr;

 
 /*
  * Here's the routine that will replace the standard error_exit method:
  */
 
 
 /*
  * Here's the routine that will replace the standard error_exit method:
  */
 

-METHODDEF(void)
-my_error_exit (j_common_ptr cinfo)
+CPP_METHODDEF(void) wx_error_exit (j_common_ptr cinfo)

 {
 {

-  /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
-  my_error_ptr myerr = (my_error_ptr) cinfo->err;
+  /* cinfo->err really points to a wx_error_mgr struct, so coerce pointer */
+  wx_error_ptr myerr = (wx_error_ptr) cinfo->err;

 
   /* Always display the message. */
   /* We could postpone this until after returning, if we chose. */
 
   /* Always display the message. */
   /* We could postpone this until after returning, if we chose. */


@@ -146,36 +173,64 @@ my_error_exit (j_common_ptr cinfo)
   longjmp(myerr->setjmp_buffer, 1);
 }
 
   longjmp(myerr->setjmp_buffer, 1);
 }
 

+void wx_jpeg_io_src( j_decompress_ptr cinfo, wxInputStream& infile )
+{
+    wx_src_ptr src;

 
 

+    if (cinfo->src == NULL) {    /* first time for this JPEG object? */
+        cinfo->src = (struct jpeg_source_mgr *)
+            (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
+            sizeof(wx_source_mgr));
+    }
+    src = (wx_src_ptr) cinfo->src;
+    src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
+    src->buffer = new JOCTET[JPEG_IO_BUFFER_SIZE];
+    src->pub.next_input_byte = NULL; /* until buffer loaded */
+    src->stream = &infile;
+
+    src->pub.init_source = wx_init_source;
+    src->pub.fill_input_buffer = wx_fill_input_buffer;
+    src->pub.skip_input_data = wx_skip_input_data;
+    src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
+    src->pub.term_source = wx_term_source;
+}
+
+
+// temporarily disable the warning C4611 (interaction between '_setjmp' and
+// C++ object destruction is non-portable) - I don't see any dtors here
+#ifdef __VISUALC__
+    #pragma warning(disable:4611)
+#endif /* VC++ */

 
 bool wxJPEGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose, int WXUNUSED(index) )
 {
     struct jpeg_decompress_struct cinfo;
 
 bool wxJPEGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose, int WXUNUSED(index) )
 {
     struct jpeg_decompress_struct cinfo;

-    struct my_error_mgr jerr;
+    struct wx_error_mgr jerr;

     JSAMPARRAY tempbuf;
     unsigned char *ptr;
     unsigned stride;
 
     image->Destroy();
     cinfo.err = jpeg_std_error( &jerr.pub );
     JSAMPARRAY tempbuf;
     unsigned char *ptr;
     unsigned stride;
 
     image->Destroy();
     cinfo.err = jpeg_std_error( &jerr.pub );

-    jerr.pub.error_exit = my_error_exit;
+    jerr.pub.error_exit = wx_error_exit;

 
     if (!verbose) cinfo.err->output_message=NULL;
 
 
     if (!verbose) cinfo.err->output_message=NULL;
 

-    /* Establish the setjmp return context for my_error_exit to use. */
+    /* Establish the setjmp return context for wx_error_exit to use. */

     if (setjmp(jerr.setjmp_buffer)) {
       /* If we get here, the JPEG code has signaled an error.
        * We need to clean up the JPEG object, close the input file, and return.
        */
     if (setjmp(jerr.setjmp_buffer)) {
       /* If we get here, the JPEG code has signaled an error.
        * We need to clean up the JPEG object, close the input file, and return.
        */

-      if (verbose) 
+      if (verbose)

         wxLogError(_("JPEG: Couldn't load - file is probably corrupted."));
         wxLogError(_("JPEG: Couldn't load - file is probably corrupted."));

+      (cinfo.src->term_source)(&cinfo);

       jpeg_destroy_decompress(&cinfo);
       if (image->Ok()) image->Destroy();
       jpeg_destroy_decompress(&cinfo);
       if (image->Ok()) image->Destroy();

-      return FALSE;
+      return false;

     }
 
     jpeg_create_decompress( &cinfo );
     }
 
     jpeg_create_decompress( &cinfo );

-    jpeg_wxio_src( &cinfo, stream );
+    wx_jpeg_io_src( &cinfo, stream );

     jpeg_read_header( &cinfo, TRUE );
     cinfo.out_color_space = JCS_RGB;
     jpeg_start_decompress( &cinfo );
     jpeg_read_header( &cinfo, TRUE );
     cinfo.out_color_space = JCS_RGB;
     jpeg_start_decompress( &cinfo );


@@ -184,9 +239,9 @@ bool wxJPEGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbos
     if (!image->Ok()) {
         jpeg_finish_decompress( &cinfo );
         jpeg_destroy_decompress( &cinfo );
     if (!image->Ok()) {
         jpeg_finish_decompress( &cinfo );
         jpeg_destroy_decompress( &cinfo );

-        return FALSE;
+        return false;

     }
     }

-    image->SetMask( FALSE );
+    image->SetMask( false );

     ptr = image->GetData();
     stride = cinfo.output_width * 3;
     tempbuf = (*cinfo.mem->alloc_sarray)
     ptr = image->GetData();
     stride = cinfo.output_width * 3;
     tempbuf = (*cinfo.mem->alloc_sarray)


@@ -199,27 +254,23 @@ bool wxJPEGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbos
     }
     jpeg_finish_decompress( &cinfo );
     jpeg_destroy_decompress( &cinfo );
     }
     jpeg_finish_decompress( &cinfo );
     jpeg_destroy_decompress( &cinfo );

-    return TRUE;
+    return true;

 }
 
 }
 

-
-
-
-

 typedef struct {
     struct jpeg_destination_mgr pub;
 
     wxOutputStream *stream;
     JOCTET * buffer;
 typedef struct {
     struct jpeg_destination_mgr pub;
 
     wxOutputStream *stream;
     JOCTET * buffer;

-} my_destination_mgr;
+} wx_destination_mgr;

 
 

-typedef my_destination_mgr * my_dest_ptr;
+typedef wx_destination_mgr * wx_dest_ptr;

 
 #define OUTPUT_BUF_SIZE  4096    /* choose an efficiently fwrite'able size */
 
 
 #define OUTPUT_BUF_SIZE  4096    /* choose an efficiently fwrite'able size */
 

-METHODDEF(void) init_destination (j_compress_ptr cinfo)
+CPP_METHODDEF(void) wx_init_destination (j_compress_ptr cinfo)

 {
 {

-    my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
+    wx_dest_ptr dest = (wx_dest_ptr) cinfo->dest;

 
     /* Allocate the output buffer --- it will be released when done with image */
     dest->buffer = (JOCTET *)
 
     /* Allocate the output buffer --- it will be released when done with image */
     dest->buffer = (JOCTET *)


@@ -229,9 +280,9 @@ METHODDEF(void) init_destination (j_compress_ptr cinfo)
     dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
 }
 
     dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
 }
 

-METHODDEF(boolean) empty_output_buffer (j_compress_ptr cinfo)
+CPP_METHODDEF(boolean) wx_empty_output_buffer (j_compress_ptr cinfo)

 {
 {

-    my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
+    wx_dest_ptr dest = (wx_dest_ptr) cinfo->dest;

 
     dest->stream->Write(dest->buffer, OUTPUT_BUF_SIZE);
     dest->pub.next_output_byte = dest->buffer;
 
     dest->stream->Write(dest->buffer, OUTPUT_BUF_SIZE);
     dest->pub.next_output_byte = dest->buffer;


@@ -239,65 +290,90 @@ METHODDEF(boolean) empty_output_buffer (j_compress_ptr cinfo)
     return TRUE;
 }
 
     return TRUE;
 }
 

-METHODDEF(void) term_destination (j_compress_ptr cinfo)
+CPP_METHODDEF(void) wx_term_destination (j_compress_ptr cinfo)

 {
 {

-    my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
+    wx_dest_ptr dest = (wx_dest_ptr) cinfo->dest;

     size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
     /* Write any data remaining in the buffer */
     if (datacount > 0)
         dest->stream->Write(dest->buffer, datacount);
 }
 
     size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
     /* Write any data remaining in the buffer */
     if (datacount > 0)
         dest->stream->Write(dest->buffer, datacount);
 }
 

-GLOBAL(void) jpeg_wxio_dest (j_compress_ptr cinfo, wxOutputStream& outfile)
+GLOBAL(void) wx_jpeg_io_dest (j_compress_ptr cinfo, wxOutputStream& outfile)

 {
 {

-    my_dest_ptr dest;
+    wx_dest_ptr dest;

 
     if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
         cinfo->dest = (struct jpeg_destination_mgr *)
             (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 
     if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
         cinfo->dest = (struct jpeg_destination_mgr *)
             (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,

-            sizeof(my_destination_mgr));
+            sizeof(wx_destination_mgr));

     }
 
     }
 

-    dest = (my_dest_ptr) cinfo->dest;
-    dest->pub.init_destination = init_destination;
-    dest->pub.empty_output_buffer = empty_output_buffer;
-    dest->pub.term_destination = term_destination;
+    dest = (wx_dest_ptr) cinfo->dest;
+    dest->pub.init_destination = wx_init_destination;
+    dest->pub.empty_output_buffer = wx_empty_output_buffer;
+    dest->pub.term_destination = wx_term_destination;

     dest->stream = &outfile;
 }
 
 bool wxJPEGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 {
     struct jpeg_compress_struct cinfo;
     dest->stream = &outfile;
 }
 
 bool wxJPEGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 {
     struct jpeg_compress_struct cinfo;

-    struct my_error_mgr jerr;
+    struct wx_error_mgr jerr;

     JSAMPROW row_pointer[1];    /* pointer to JSAMPLE row[s] */
     JSAMPLE *image_buffer;
     int stride;                /* physical row width in image buffer */
 
     cinfo.err = jpeg_std_error(&jerr.pub);
     JSAMPROW row_pointer[1];    /* pointer to JSAMPLE row[s] */
     JSAMPLE *image_buffer;
     int stride;                /* physical row width in image buffer */
 
     cinfo.err = jpeg_std_error(&jerr.pub);

-    jerr.pub.error_exit = my_error_exit;
+    jerr.pub.error_exit = wx_error_exit;

 
     if (!verbose) cinfo.err->output_message=NULL;
 
 
     if (!verbose) cinfo.err->output_message=NULL;
 

-    /* Establish the setjmp return context for my_error_exit to use. */
-    if (setjmp(jerr.setjmp_buffer)) 
+    /* Establish the setjmp return context for wx_error_exit to use. */
+    if (setjmp(jerr.setjmp_buffer))

     {
         /* If we get here, the JPEG code has signaled an error.
          * We need to clean up the JPEG object, close the input file, and return.
          */
     {
         /* If we get here, the JPEG code has signaled an error.
          * We need to clean up the JPEG object, close the input file, and return.
          */

-         if (verbose) 
+         if (verbose)

             wxLogError(_("JPEG: Couldn't save image."));
          jpeg_destroy_compress(&cinfo);
             wxLogError(_("JPEG: Couldn't save image."));
          jpeg_destroy_compress(&cinfo);

-         return FALSE;
+         return false;

     }
 
     jpeg_create_compress(&cinfo);
     }
 
     jpeg_create_compress(&cinfo);

-    jpeg_wxio_dest(&cinfo, stream);
+    wx_jpeg_io_dest(&cinfo, stream);

 
     cinfo.image_width = image->GetWidth();
     cinfo.image_height = image->GetHeight();
     cinfo.input_components = 3;
     cinfo.in_color_space = JCS_RGB;
     jpeg_set_defaults(&cinfo);
 
     cinfo.image_width = image->GetWidth();
     cinfo.image_height = image->GetHeight();
     cinfo.input_components = 3;
     cinfo.in_color_space = JCS_RGB;
     jpeg_set_defaults(&cinfo);

+
+    // TODO: 3rd parameter is force_baseline, what value should this be?
+    // Code says: "If force_baseline is TRUE, the computed quantization table entries
+    // are limited to 1..255 for JPEG baseline compatibility."
+    // 'Quality' is a number between 0 (terrible) and 100 (very good).
+    // The default (in jcparam.c, jpeg_set_defaults) is 75,
+    // and force_baseline is TRUE.
+    if (image->HasOption(wxT("quality")))
+        jpeg_set_quality(&cinfo, image->GetOptionInt(wxT("quality")), TRUE);
+
+    // sets the resolution fields in the output file
+    if (image->HasOption(wxIMAGE_OPTION_RESOLUTION))
+    {
+        cinfo.X_density =
+        cinfo.Y_density = (UINT16)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTION);
+    }
+
+    // sets the resolution unit field in the output file
+    // wxIMAGE_RESOLUTION_INCHES for inches
+    // wxIMAGE_RESOLUTION_CM for centimeters
+    if (image->HasOption(wxIMAGE_OPTION_RESOLUTIONUNIT))
+    {
+        cinfo.density_unit = (UINT8)image->GetOptionInt(wxIMAGE_OPTION_RESOLUTIONUNIT);
+    }
+

     jpeg_start_compress(&cinfo, TRUE);
 
     stride = cinfo.image_width * 3;    /* JSAMPLEs per row in image_buffer */
     jpeg_start_compress(&cinfo, TRUE);
 
     stride = cinfo.image_width * 3;    /* JSAMPLEs per row in image_buffer */


@@ -309,17 +385,21 @@ bool wxJPEGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
     jpeg_finish_compress(&cinfo);
     jpeg_destroy_compress(&cinfo);
 
     jpeg_finish_compress(&cinfo);
     jpeg_destroy_compress(&cinfo);
 

-    return TRUE;
+    return true;

 }
 
 }
 

+#ifdef __VISUALC__
+    #pragma warning(default:4611)
+#endif /* VC++ */

 
 bool wxJPEGHandler::DoCanRead( wxInputStream& stream )
 {
     unsigned char hdr[2];
 
 
 bool wxJPEGHandler::DoCanRead( wxInputStream& stream )
 {
     unsigned char hdr[2];
 

-    stream.Read(&hdr, 2);
-    stream.SeekI(-2, wxFromCurrent);
-    return (hdr[0] == 0xFF && hdr[1] == 0xD8);
+    if ( !stream.Read(hdr, WXSIZEOF(hdr)) )
+        return false;
+
+    return hdr[0] == 0xFF && hdr[1] == 0xD8;

 }
 
 #endif   // wxUSE_STREAMS
 }
 
 #endif   // wxUSE_STREAMS