[poppler] Toward to JBIG2 support in CairoOutputDev

[suzuki toshiya]

Thanks! Should I submit some data including JBIG2 images?

Regards,
mpsuzuki


(2015/01/12 20:14), Adrian Johnson wrote:
> The latest patch looks good. I'll wait a week before committing to see
> if anyone else has any comments. This will give me time to do some
> testing of the patch.
> 
> On 11/01/15 23:05, suzuki toshiya wrote:
>> Dear Adrian,
>>
>> OK - considering that there is a lag to the day that Linux
>> distribution ship the poppler stable branch including
>> CairoOutputDev with JBIG2 support even if I support some
>> snapshot of Cairo in current development branch of poppler
>> (and there would be no need to support Cairo snapshot in
>> the day), I decided to follow original version checking.
>>
>> Also I removed the default value (NULL) for Ref object to
>> JBIG2Stream constructor and removed NULL pointer checking
>> in JBIG2Stream constructor (as same as the argument to pass
>> Globals object).
>>
>> I replaced "st" in CairoOutputDev, by "status".
>>
>> Here I attached revised patch - oh, I'm quite sorry, my
>> previous posts were misunderstanding this year as 2014.
>>
>> Regards,
>> mpsuzuki
>>
>> Adrian Johnson wrote:
>>> On 08/01/15 13:35, suzuki toshiya wrote:
>>>> Dear Adrian,
>>>>
>>>> Great Thank you for prompt review! I attached the revised patch,
>>>> but please let me discuss a few points.
>>>>
>>>> Adrian Johnson wrote:
>>>>> On 07/01/15 02:58, suzuki toshiya wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> Here I submit a preliminary patch for git head,
>>>>>> which enables JBIG2 embedding to PDF surface via Cairo.
>>>>> +static cairo_status_t setJBIG2GlobalsIdByRefNums(int refNum, int
>>>>> refGen,
>>>>> +                                                 cairo_surface_t
>>>>> *image)
>>>>> +{
>>>>> +  GooString *globalsStrId;
>>>>> +  char *idBuffer;
>>>>> +  cairo_status_t st;
>>>>> +
>>>>> +
>>>>> +  globalsStrId = new GooString;
>>>>> +  globalsStrId->appendf("{0:d}-{1:d}", refNum, refGen);
>>>>> +  idBuffer = copyString(globalsStrId->getCString());
>>>>> +  st = cairo_surface_set_mime_data (image,
>>>>> CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID,
>>>>>
>>>>> The cairo JBIG2 mime types are new to 1.14.0 so will need to be
>>>>> inside a
>>>>> #if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 14, 0).
>>>> If it's acceptable, I want to use the conditional like
>>>>     #ifdef CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID
>>>> The official release of cairo including JBIG2 support is 1.14.0,
>>>> however, some distributions use a snapshot before 1.14 which
>>>> supports JBIG2. For example, Ubuntu 14.04 (long time support)
>>>> ships with 1.13.0~20140204.
>>>>    
>>>> http://packages.ubuntu.com/search?suite=trusty&section=all&arch=any&keywords=libcairo2&searchon=names
>>>>
>>>>
>>>> It includes JBIG2 support. Thus I prefer checking by the JBIG2
>>>> macros, instead of the version checking.
>>> I'm not keen on making an exception for this case. The target audience
>>> for this is very small. It would only help users that compile a new
>>> version of poppler on an old distribution without also recompiling
>>> cairo. JBIG2 support for pdftocairo is a very minor feature that not
>>> many people would be using (so far no one else has requested this
>>> feature).
>>>
>>> If you really want to support distributions using a cairo 1.13 snapshot
>>> I suggest adding a comment before the first occurrence of
>>> #ifdef CAIRO_MIME_TYPE_JBIG2_GLOBAL_ID to explain why the version macro
>>> is not used. Also include
>>> "#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 14, 0)" in the comment so
>>> that:
>>> a) searching for CAIRO_VERSION will find it, and
>>> b) to document that JBIG2 support is in 1.14 or later.
>>>
>>>> BTW, when the string for UNIQUE_ID is constructed, its syntax
>>>> is RefGen-RefNum. In PDF data, RefNum then RefGen is popular
>>>> syntax. Is there any reason why the order is reverted?
>>> No reason. Feel free to change it to num-gen order.
>>>
>>>>> +GBool CairoOutputDev::setMimeDataForJBIG2Globals(Stream  *str,
>>>>> +                                                 cairo_surface_t
>>>>> *image)
>>>>> +{
>>>>> +  JBIG2Stream *jbig2Str = static_cast<JBIG2Stream *>(str);
>>>>> +  Object* globalsStr = jbig2Str->getGlobalsStream();
>>>>> +  char *globalsBuffer;
>>>>> +  int globalsLength;
>>>>> +
>>>>> +  // According to PDF spec, Globals should be stream (or nothing)
>>>>> +
>>>>> +  if (globalsStr->isNull())
>>>>> +    return gTrue;
>>>>> +
>>>>> +  if (!globalsStr->isStream())
>>>>> +    return gFalse;
>>>>> +
>>>>> +  // See JBIG2Stream constructor for valid reference number
>>>>> +  if (!jbig2Str->getGlobalsStreamRefNum())
>>>>> +    return gFalse;
>>>>>
>>>>> The globalsStr->isStream() check should be sufficient. The reference
>>>>> number should always be valid of the global stream is valid.
>>>> Umm. Requesting "both of JBIG2Stream::globalsStream and Ref to
>>>> it must be always valid as far as GlobalsStream is used" is
>>>> intuitive solution, but public JBIG2Stream constructor has not
>>>> requested the Ref to GlobalsStream before in earlier version.
>>>>
>>>> If some developers use JBIG2Stream constructor with valid
>>>> GlobalsStream but without Ref to it (as the syntax before my
>>>> patch), there is the situation that JBIG2Stream::globalsStream
>>>> is valid but Ref to it is invalid (if I supply the default
>>>> value for the argument to pass Ref). How do we detect or prevent
>>>> such case?
>>>>
>>>> A) Supplying the default value (NULL pointer) in the argument
>>>> to pass the Ref, and JBIG2Stream returns an error when
>>>> globalsStream is valid stream but its Ref is not passed - and
>>>> prevent the case that globalsStream is valid but its Ref is
>>>> invalid.
>>>>
>>>> B) Not supplying the default value, and prevent the construction
>>>> without the Ref to the globalsStream.
>>>>
>>>> C) Add new boolean value in JBIG2Stream class, to indicate if
>>>> Ref to globalsStream is explicitly set.
>>>>
>>>> D) Initialize Ref with irregular value (e.g. 0,0 or 0,65535)
>>>> internally when Ref is not passed, and deal the case as Ref to
>>>> the globalsStream is not initialized (my last patch design)
>>>>
>>>> Which is the best? Or, no need to case such case?
>>> JBIG2Stream is not part of the public API so there is no need to
>>> preserve compatibility.
>>>
>>> Something else I just noticed - could you rename "st" to "status".
>>> CairoOutputdev.cc always uses the name "status" for cairo status so we
>>> should be consistent with this convention.
>>>
>>
>