Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Jeremy Geelan, Maureen O'Gara, Nancy Y. Nee, Tad Anderson

Related Topics: Adobe Flex, ColdFusion

Adobe Flex: Tutorial

Creating Layered PDFs with Escape Calls to the PDF Converter Printer

PDF Layers are called Optional Content within the PDF specifications

Background information
PDF Layers are called Optional Content within the PDF specifications. This is a feature that was added as of PDF-1.5 (Acrobat 6.) A layer is identified by an identifier and a title. Only the layer title is visible to the end-user of the PDF document. Layers can be structured as a tree or as a hierarchy of layers.  Here is a sample Optional Content object in a PDF:

9 0 obj <</Type/OCG/Name(Blue Layer) >> endobj

Each page using this layer should add the layer to its list of resources, for example:

6 0 obj <</Type /Page /Parent 3 0 R /MediaBox [0 0 612 792 ] /Contents [7 0 R ]
/Resources << /ProcSet [/PDF /Text] /Font <</F10 10 0 R >>
/Properties <</OC9 9 0 R >>
>> >> endobj


OC9 is the layer ID (Blue Layer) and is the layer title (strings in PDF are surrounded by parenthesis). To indicate that various objects within the page content belong to specific layers, the following syntax is used:

% start the Blue Layer that contains the text: Page 1
/OC /OC9 BDC
BT /F10 5.76  Tf 1 0 0 1 24 745.56 Tm 0.026  Tc -0.067  Tw (Page 1) Tj ET

% start a sub-layer that will contain a filled rectangle
/OC /OC11 BDC
n 1 g 96 326.96 35.76 -6.6 re f*
% end of sub-layer 1
EMC

% start another sub-layer that will contain another filled rectangle
/OC /OC13 BDC
n 1 g 96 526.96 35.76 -6.6 re f*
% end of sub-layer 2
EMC


%end of blue layer
EMC


Although the code shows one parent layer and two nested layers (contained within the parent layer), this is not enough to define the hierarchy of layers. The Order string is used to determine the hierarchy of layers. The Order string is part of the document Catalog. The Order string for the above PDF sample should look like this:

/Order [ 9 0 R [11 0 R 13 0 R] ]

The object IDs are needed to create a proper order string. The order string can also contain a parent node that is not a layer but only a container for other layers. In the example above we could have all the layers below to one parent layer called (Layered PDF) by using:

/Order [ (Layered PDF)  9 0 R [11 0 R 13 0 R]  ]

It is important that the Order string matches the order of layers as they appear in the page content, otherwise the PDF viewer will not be able to properly “show and hide” layers with their sub-layers.

Note: There is an inconsistency in the PDF specifications related to defining nodes that are parents of other layers. To have a Layered PDF as the parent of layer 9, we do not use [(Layered PDF) [9 0 R] ] as one might expect but [(Layered PDF) 9 0 R] as if the 2 nodes were on the same level.

Creating Groups of Layers
The PDF format allows creating groups of mutually exclusive layers where showing one layer will automatically hide the other. These are called radio-button groups and defined using the RBGroups PDF keyword. One can also define which layers are visible by default and which are hidden, for example:

/RBGroups [[ 11 0 R 13 0 R]]  /ON[ 11 0 R] /OFF [13 0 R] indicates that layers 11 and 13 are grouped and that layer 11 is visible by default whereas 13 is invisible.

Dynamically Creating Layers using the Amyuni PDF Converter
External developers need to be aware of layer titles only. The layers IDs and object numbers are not significant to the developer, so the implemented API will only use layer titles to insert layers and define the layer hierarchy.

Layers can be inserted within a PDF file while the document is being printed by calling Escape sequences. Escape sequences are GDI artifacts that enable developers to send custom data to a printer driver.

Checking that the Printer supports PDF Layers
The first step to start adding layers is to check that the printer has support for the escape sequences that are defined by Amyuni. The following calls are needed include:

// check if PDF printer supports layers
#define ESCAPE_SETLAYER        248

CHAR    technology[4];
int escape = ESCAPE_SETLAYER;
ExtEscape( hDC, GETTECHNOLOGY, 0, NULL, sizeof(technology), (LPSTR)technology
);

// the technology should be PDF
if ( lstrcmp(technology, "PDF") )
{
MessageBox( 0, "Not an Amyuni PDF driver", "Error", MB_ICONERROR );
}

// and support the SETLAYER escape
if ( !ExtEscape( hDC, QUERYESCSUPPORT, sizeof(escape), (LPCSTR)&escape, 0,
NULL ) )   
{
MessageBox( 0, "Not an Amyuni PDF driver", "Error", MB_ICONERROR );
}

GETTECHNOLOGY and QUERYESCSUPPORT are escape sequences that are predefined by Windows GDI. ESCAPE_SETLAYER is a custom escape that is processed by the Amyuni printer.

The SETLAYER escape takes one parameter which is a Unicode string, The escape can be wrapped into a helper function such as:

void SetLayer( HDC hDC, LPWSTR LayerInfo )
{
switch ( ExtEscape( hDC, ESCAPE_SETLAYER, (int)((wcslen(LayerInfo) + 1)
* sizeof(LayerInfo[0])), (LPCSTR)LayerInfo, 0, NULL ) )
{
default:
// positive return indicates success
case 0:
// no error
return;

case -1:
// error occured, closing a layer when none was open
break;

case -2:
// memory allocation error (low memory or invalid string)
break;
}
}

The same escape call is used to start a layer or sub-layer, end a layer or define the hierarchy of layers.

Setting the Hierarchy of Layers
The order or hierarchy of layers is sent to the PDF printer using the SETLAYER escape before the call to StartDoc. It can actually be called anytime during the printing as long as the call is made outside of a StartPage/EndPage block but before the EndDoc is called. The advantage of setting the hierarchy before StartDoc is that it allows the PDF printer to expect layer support and switch the file header to PDF-1.5.

If the hierarchy of layers is not known before the call the StartDoc, the developer can call SetLayer( L"" ) with an empty string before the call to StartDoc simply to instruct the PDF printer to output PDF-1.5 header. The order string should contain the titles of all the layers and their hierarchy, all in Unicode format. E.g.:

// set the order and hierrachy of layers
SetLayer( hDC, L"/Order[(Blue Layer)[(Blue Layer - 1)(Blue Layer - 2)](Red
Layer)(Green Layer)]"
);

This will produce a layer structure like this:



To group layers within radio-button groups, the /RBGroups, /ON and /OFF entries should be added to the call above. This code for e.g. will make the red and green layers as part of a group:

// set the order and radio/button groups of layers
SetLayer( hDC, L"/Order[(Blue Layer)[(Blue Layer - 1)(Blue Layer - 2)](Red
Layer)(Green Layer)]" \
L"/RBGroups[[(Red Layer)(Green Layer)]]/OFF[(Red Layer)]/ON[(Green Layer)]"

);

Drawing Objects within Layers
Within a StartPage/EndPage sequence of calls, calling SetLayer with a valid layer title will start a new layer and place all subsequent drawing instructions within that layer. Calling SetLayer with an empty string will end the last layer. If multiple layers are nested, multiple calls to SetLayer with an empty string are needed to close all layers.

If all layers are not closed at the call to EndPage, the PDF printer will automatically close all open layers, for example:


// start parent layer
SetLayer( hDC, L"Blue Layer" );
SetTextColor( hDC, RGB(0, 0, 255) );
TextOut( hDC, 200, yPos, buf, lstrlen(buf) );
yPos += 200;

// start blue sub-layer 1
SetLayer( hDC, L"Blue Layer - 1" );
SetTextColor( hDC, RGB(0, 0, 128) );
TextOut( hDC, 800, yPos, "Blue Layer - 1", lstrlen("Blue Layer - 1") );
yPos += 200;
SetLayer( hDC, L"" );    // close blue sub-layer 1
SetLayer( hDC, L"" );    // close blue parent layer

The sequence of opening and closing layers should be consistent with the order string for the PDF viewer to show or hide layers with their sub-layers in a consistent way.

The contents for this post were provided by Dany Amiouny using the Amyuni PDF Converter developer tool.

Please visit us at www.amyuni.com to learn more about Amyuni Developer Pro tools or our Professional Services page to contact one of our qualified PDF experts.

More Stories By Amyuni Tech

Franc Gagnon is a technical copywriter for Amyuni Technologies–a PDF solution provider. Amyuni products are integrated into applications used worldwide. The company's software tools are the PDF engines behind several leading business applications created by large software companies such as Intuit, Sage, CaseWare and many more.

@ThingsExpo Stories
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change t...
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
Amazon has gradually rolled out parts of its IoT offerings, but these are just the tip of the iceberg. In addition to optimizing their backend AWS offerings, Amazon is laying the ground work to be a major force in IoT - especially in the connected home and office. In his session at @ThingsExpo, Chris Kocher, founder and managing director of Grey Heron, explained how Amazon is extending its reach to become a major force in IoT by building on its dominant cloud IoT platform, its Dash Button strat...
industrial company for a multi-year contract initially valued at over $4.0 million. In addition to DataV software, Bsquare will also provide comprehensive systems integration, support and maintenance services. DataV leverages advanced data analytics, predictive reasoning, data-driven diagnostics, and automated orchestration of remediation actions in order to improve asset uptime while reducing service and warranty costs.
Vidyo, Inc., has joined the Alliance for Open Media. The Alliance for Open Media is a non-profit organization working to define and develop media technologies that address the need for an open standard for video compression and delivery over the web. As a member of the Alliance, Vidyo will collaborate with industry leaders in pursuit of an open and royalty-free AOMedia Video codec, AV1. Vidyo’s contributions to the organization will bring to bear its long history of expertise in codec technolo...