diff options
Diffstat (limited to 'generic/tkImgGIF.c')
| -rw-r--r-- | generic/tkImgGIF.c | 46 |
1 files changed, 21 insertions, 25 deletions
diff --git a/generic/tkImgGIF.c b/generic/tkImgGIF.c index 409300c..e7f4582 100644 --- a/generic/tkImgGIF.c +++ b/generic/tkImgGIF.c @@ -963,9 +963,9 @@ ReadImage( * Last pass reset the decoder, so the first code we see * must be a singleton. Seed the stack with it, and set up * the old/first code pointers for insertion into the - * string table. We can't just roll this into the - * clearCode test above, because at that point we have not - * yet read the next code. + * codes table. We can't just roll this into the clearCode + * test above, because at that point we have not yet read + * the next code. */ *top++ = append[code]; @@ -976,11 +976,11 @@ ReadImage( inCode = code; - if (code == maxCode) { + if ((code == maxCode) && (maxCode < (1 << MAX_LWZ_BITS))) { /* * maxCode is always one bigger than our highest assigned * code. If the code we see is equal to maxCode, then we - * are about to add a new string to the table. ??? + * are about to add a new entry to the codes table. */ *top++ = firstCode; @@ -989,7 +989,7 @@ ReadImage( while (code > clearCode) { /* - * Populate the stack by tracing the string in the string + * Populate the stack by tracing the code in the codes * table from its tail to its head */ @@ -998,28 +998,24 @@ ReadImage( } firstCode = append[code]; - /* - * If there's no more room in our string table, quit. - * Otherwise, add a new string to the table - */ - - if (maxCode >= (1 << MAX_LWZ_BITS)) { - return TCL_OK; - } - - /* - * Push the head of the string onto the stack. - */ + /* + * Push the head of the code onto the stack. + */ - *top++ = firstCode; + *top++ = firstCode; - /* - * Add a new string to the string table - */ + if (maxCode < (1 << MAX_LWZ_BITS)) { + /* + * If there's still room in our codes table, add a new entry. + * Otherwise don't, and keep using the current table. + * See DEFERRED CLEAR CODE IN LZW COMPRESSION in the GIF89a + * specification. + */ - prefix[maxCode] = oldCode; - append[maxCode] = firstCode; - maxCode++; + prefix[maxCode] = oldCode; + append[maxCode] = firstCode; + maxCode++; + } /* * maxCode tells us the maximum code value we can accept. If |