If you are a Flex developer or wanting to learn Flex, i highly recommend you look at Adobe’s video training course called Flex 4 beta in a Week.

The course is broken up over 5 days as follows:

Day 1 – Exploring the basic, Introducing object-orientated programming and Understanding components and layouts
Day 2 – Handling events, Validating and formatting data, Navigating application content and Animating components and states
Day 3 – Controlling text display, Controlling visual display and CSS and Skinning Spark components
Day 4 – Extending events, Accessing remote data and Creating a typed data model
Day 5 – Displaying data with the DataGroup container, Displaying Data with the DataGrid control and Deploying Flex and AIR Applications

Seasoned Flex developers may only find some of these areas useful, such as the Skinning Spark components and Displaying data with the DataGroup container (Coming soon).

This project required me to implement functionality that would allow the end user to export groups of images to PDF. The PDF needed to be high quality, 300 ppi (pixels per inch). After some searching I came across the AlivePDF website which appeared to be perfect for my requirements. Initially after using AlivePDF to generate a few PDFs, I couldn’t believe how easy it was to use and I thought that I had found Utopia. My joy however was short lived after the following error message was received:

AlivePDF had no alpha channel support for PNGs and the PNG encoder provided by Adobe always returns a PNG with an alpha channel. Even if you turned off the transparency you will get back a 32 bit ARGB PNG.

I continued searching for someone who had a method of successfully removing the alpha channel but my search proved fruitless. Hence I decided to do my own research into PNGs and found the following:

A valid PNG consists of:

PNG signature
IHDR chunk (only one)
IDAT chunk (one or more)
IEND chunk (only one)

The PNG signature:

89 50 4E 47 0D 0A 1A 0A.

The IHDR image header:

The IDAT chunks contain the image data.
The IEND chunk marks the end of the PNG.

The colour type under the IHDR chunk needs to be mentioned here as that is where the image type is defined.

After familiarizing myself with PNGs, I revisited Adobe’s PNGEncoder.as class again and eventually managed to make certain changes that allowed the removal of the alpha channel all together.

After all the research this ended up being a lot easier than I had originally thought, all that I needed to do was change the colour type and extract the RGB values. Adobe’s colour type was 6 (True colour with alpha) I changed it to 2 (True colour only). Next I needed to isolate and extract the RGB values, this was done with a bitwise right shift operation and a bitwise AND operation.

// Build IHDR chunk
 
var IHDR:ByteArray = new ByteArray();
IHDR.writeInt(w);
IHDR.writeInt(h);
IHDR.writeUnsignedInt(0x08020000); // True colour (no alpha)
IHDR.writeByte(0);
writeChunk(png, 0x49484452, IHDR);
 
// Isolate RGB values
 
for (var j:int = 0; j < w; j++)
{
	p = img.getPixel(j, i);
	IDAT.writeByte(p >> 16 & 0xFF);
	IDAT.writeByte(p >> 8 & 0xFF);
	IDAT.writeByte(p & 0xFF);
}

The changes implemented resulted in the removal of the Alpha channel which allowed me to successfully embedded the encoded PNG image into a PDF with AlivePDF. This was the first of many problems I had working with PDFs, maybe you will get to read about the others in the not too distant future. Attached below is a sample application that will embed a PNG into a PDF.

I have listed all the tutorials, videos and screencasts below.

Adobe Flash Catalyst

Get Started
Learn about Flash Catalyst

• Video: Introducing Flash Catalyst
  Discover what you can do with this new interaction design tool for creating interactive experiences.
• Video: Wire Framing in Flash Catalyst
  Learn how to quickly wireframe a design concept in Flash Catalyst.
• Notes: Learn about Flash Catalyst
  Refer to these feature notes that detail what you can do with this interaction design tool.

Start Building Your First Flash Catalyst Application

• Video: Create your First Application with Flash Catalyst
  Let Ty Voilter step you through the process of prototyping an interactive application.
• Tutorial: Start Designing in Flash Catalyst
  Learn to create a simple SWF content from a Photoshop design.
• Tutorial: Build a Data-Centric Application Using Flash Catalyst and Flash Builder 4
  Learn to create a browser-based address book application from an Illustrator design.

Get Better
Explore Flash Catalyst Workflows

• Video: Exporting from Fireworks CS4 to Flash Catalyst
  Presenter: Doug Winnie; Adobe
• Video: Use Native Fireworks CS4 Files in Flash Catalyst
  Presenter: Doug Winnie; Adobe

Work with Flash Catalyst

• Video: Create a Data List in Flash Catalyst
  Presenter: Nate Bishop; Adobe
• Video: Create Animations in Flash Catalyst
  Presenter: Ty Voilter; Adobe
• Video: Distribute Objects to States with Flash Catalyst
  Presenter: Doug Winnie; Adobe
• Video: Sharing Flash Catalyst Libraries
  Presenter: Doug Winnie; Adobe

Learn from the Community

• Video: Flash Catalyst Preview
  Presenter: Mordy Golding; Lynda.com
• Screencast: Using Flash Catalyst and Flex 4 beta 1 – Part 1:  Design a Twitter search app
  Presenter: Lee Brimelow; gotoAndLearn()
• Screencast: Using Flash Catalyst and Flex 4 beta 1 – Part 2: Hook up the app to live data
  Presenter: Lee Brimelow; gotoAndLearn()
• Screencast: Introducing Flash Catalyst – Part 1: Good practices for preparing Illustrator files
  Presenter: Garth Braithwaite; InsideRIA
• Screencast: Introducing Flash Catalyst – Part 2: Import and export artwork and libraries
  Presenter: Garth Braithwaite; InsideRIA
• Tutorial: Adobe Flash Catalyst: A Designer’s Ticket to the Interactive World
  Andrew Faulkner; Peachpit