bug fix for wxBufferedInputStream::LastCount() after Read()

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

diff --git a/src/common/gifdecod.cpp b/src/common/gifdecod.cpp
index 923685e552d0838a52516db4fca9263ede7bc290..f287947799cd8b7538956546883fbadc2eb3c67b 100644 (file)
--- a/src/common/gifdecod.cpp
+++ b/src/common/gifdecod.cpp
@@ -126,6 +126,24 @@ bool wxGIFDecoder::ConvertToImage(wxImage *image) const
     else
         image->SetMask(FALSE);
 
+#if wxUSE_PALETTE
+    if (pal)
+    {
+        unsigned char r[256];
+        unsigned char g[256];
+        unsigned char b[256];
+
+        for (i = 0; i < 256; i++)
+        {
+            r[i] = pal[3*i + 0];
+            g[i] = pal[3*i + 1];
+            b[i] = pal[3*i + 2];
+        }
+
+        image->SetPalette(wxPalette(256, r, g, b));
+    }
+#endif // wxUSE_PALETTE
+
     /* copy image data */
     for (i = 0; i < (GetWidth() * GetHeight()); i++, src++)
     {
@@ -317,18 +335,17 @@ int wxGIFDecoder::getcode(int bits, int ab_fin)
 //
 int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits)
 {
-    int ab_prefix[4096];        /* alphabet (prefixes) */
-    int ab_tail[4096];          /* alphabet (tails) */
-    int stack[4096];            /* decompression stack */
-
-    int ab_clr;                 /* clear code */
-    int ab_fin;                 /* end of info code */
-    int ab_bits;                /* actual symbol width, in bits */
-    int ab_free;                /* first free position in alphabet */
-    int ab_max;                 /* last possible character in alphabet */
-    int pass;                   /* pass number in interlaced images */
-    int pos;                    /* index into decompresion stack */
-    unsigned int x, y;          /* position in image buffer */
+    int *ab_prefix = new int[4096]; /* alphabet (prefixes) */
+    int *ab_tail = new int[4096];   /* alphabet (tails) */
+    int *stack = new int[4096];     /* decompression stack */
+    int ab_clr;                     /* clear code */
+    int ab_fin;                     /* end of info code */
+    int ab_bits;                    /* actual symbol width, in bits */
+    int ab_free;                    /* first free position in alphabet */
+    int ab_max;                     /* last possible character in alphabet */
+    int pass;                       /* pass number in interlaced images */
+    int pos;                        /* index into decompresion stack */
+    unsigned int x, y;              /* position in image buffer */
 
     int code, readcode, lastcode, abcabca;
 
@@ -435,6 +452,46 @@ int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits)
                 {
                     /* non-interlaced */
                     y++;
+/*
+Normally image decoding is finished when an End of Information code is
+encountered (code == ab_fin) however some broken encoders write wrong
+"block byte counts" (The first byte value after the "code size" byte),
+being one value too high. It might very well be possible other variants
+of this problem occur as well. The only sensible solution seems to
+be to check for clipping.
+Example of wrong encoding:
+(1 * 1 B/W image, raster data stream follows in hex bytes)
+
+02  << B/W images have a code size of 2
+02  << Block byte count
+44  << LZW packed
+00  << Zero byte count (terminates data stream)
+
+Because the block byte count is 2, the zero byte count is used in the
+decoding process, and decoding is continued after this byte. (While it
+should signal an end of image)
+
+It should be:
+02
+02
+44
+01  << When decoded this correctly includes the End of Information code
+00
+
+Or (Worse solution):
+02
+01
+44
+00
+(The 44 doesn't include an End of Information code, but at least the
+decoder correctly skips to 00 now after decoding, and signals this
+as an End of Information itself)
+*/
+                    if (y >= img->h)
+                    {
+                        code = ab_fin;
+                        break;
+                    }
                 }
             }
         }
@@ -444,6 +501,10 @@ int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits)
     }
     while (code != ab_fin);
 
+    delete [] ab_prefix ;
+    delete [] ab_tail ;
+    delete [] stack ;
+
     return 0;
 }
 
@@ -476,10 +537,11 @@ int wxGIFDecoder::ReadGIF()
     int           ncolors, bits, interl, transparent, disposal, i;
     long          size;
     long          delay;
-    unsigned char type;
+    unsigned char type = 0;
     unsigned char pal[768];
     unsigned char buf[16];
-    GIFImage      **ppimg, *pimg, *pprev;
+    GIFImage      **ppimg;
+        GIFImage      *pimg, *pprev;
 
     /* check GIF signature */
     if (!CanRead())
@@ -569,8 +631,12 @@ int wxGIFDecoder::ReadGIF()
 
             /* fill in the data */
             m_f->Read(buf, 9);
+            pimg->left = buf[0] + 256 * buf[1];
+            pimg->top = buf[2] + 256 * buf[3];
+/*
             pimg->left = buf[4] + 256 * buf[5];
             pimg->top = buf[4] + 256 * buf[5];
+*/
             pimg->w = buf[4] + 256 * buf[5];
             pimg->h = buf[6] + 256 * buf[7];
             interl = ((buf[8] & 0x40)? 1 : 0);
@@ -627,6 +693,9 @@ int wxGIFDecoder::ReadGIF()
     /* try to read to the end of the stream */
     while (type != 0x3B)
     {
+        if (!m_f->IsOk())
+            return wxGIF_TRUNCATED;
+            
         type = (unsigned char)m_f->GetC();
 
         if (type == 0x21)