PRODUCTS: ECW Escalator Documentation

Stellar Science presents ECW Escalator, an Adobe Photoshop File Format Plug-in that allows you to read ECW imagery directly into Photoshop and other host image processing applications.

Normal Usage
ECW Escalator is a File Format plug-in that conforms to Adobe Photoshop's plug-in API. If you have an application that accepts these types of plug-ins then ECW Escalator will provide you with the ability to directly read in ECW imagery without performing off-line file conversions. Examples of applications that support Adobe's File Format Plug-in API are:

  • Adobe Photoshop CS2/CS3/CS4(x86)
  • Adobe Photoshop Elements 5.0/6.0/7.0

ECW Escalator is included as a complimentary bonus with both the NITF Escalator and J2K Escalator Photoshop file format plug-in products.

Routine usage of ECW Escalator is simple, though the user interface often leaves much to be desired. Once the plug-in has been installed into a host application, you can open an ECW image by selecting the File|Open As... command provided by the host. Note that, because Photoshop is not accustomed to accessing remote files via the ecwp protocol, it is unlikely that selecting the File|Open... command will work properly. Use File|Open As... instead.

A File chooser dialog will then open. Select the ECW Escalator type in the Open As combo box. You may then select any data file on your system. The file you select here will ultimately be ignored by ECW Escalator. After making this place holder selection, NITF Escalator will allow you to select the ECWP URL you would like to load by showing the following dialog:

You may then enter the URL of your image file in the box provided. ECWP URLs usually begin with the following characters: "ecwp://". ECW images can be quite large when they are uncompressed. NITF Escalator is designed to handle large images but there is a limit since the entire image must be read in and passed back to the host application one block at a time. Host applications with sophisticated caching schemes, like Photoshop CS2, can overcome some memory limitations but the loading process can be painfully slow. The ECW Escalator team tested the plug-in with an ECW image that contained over 100,000,000 pixels and it loaded in couple of minutes. Afterwards, the tester was able to quickly pan and zoom the ECW image.

Intensity Scaling
ECW Images can come in a variety of data types. ECW Escalator can handle nearly all of them, including images that contain the following pixel types:

  • 1 Bit Boolean
  • 8 Bit Unsigned Integer
  • 8 Bit Signed Integer
  • 16 Bit Unsigned Integer
  • 16 Bit Signed Integer

Unfortunately, the Adobe Photoshop API is not quite as flexible when it comes to data types. The API only supports 8 Bit Unsigned Integer, 16 Bit Unsigned Integer, and 32 Bit Precision Real Numbers. When ECW Escalator encounters an image that is not one of these types, it will convert the image into an accepted type for you. This may require that the data be intensity scaled so that you will actually be able to see some relevant image detail. The following dialog will allow you to control the details of this transform if you wish:

Each pixel value in the ECW image will be multiplied by the specified Scale, added to the specified Bias, and then clamped to the range of New Data Type where New Data Type is one of Photoshop's acceptable pixel types. ECW Escalator will sample the image and determine default values that will normally behave well. However, if you open an image and it's all black or all white, you may need to re-open the image and adjust these values accordingly.

Other Warnings
There are other types of ECW images that deserve special mention and ECW Escalator will point them out when it finds one. For example, you may see a warning box with one of the following messages when loading an image:

  • The selected image contains X channels. Photoshop only allows a maximum of 56 channels. ECW Escalator has truncated excess channels so that the image could be loaded - A single ECW image can contain many channels whereas Photoshop will only handle 56 channel images. The current version of ECW Escalator handles this case by slicing off all channels past the 56th one. Future versions of the plug-in may allow you more control over which channels you would like to view.

Advanced Settings
If you have permissions and the know-how to edit the registry on your computer, there are a few ECW Escalator settings that you may adjust. If you are unsure what the registry is or how to edit, it's best to skip this chapter. Modifying your operating system's registry improperly can harm your computer. Future versions of ECW Escalator may offer a more user-friendly way to modify these settings. For now though, they can only be turned on or off by manually editing the registry. Available settings are:

  • No Warning Boxes: The Other Warnings section of this document describes a number of warning boxes that can pop up while loading a ECW image. Create a string value in the registry with the following name to turn these warnings off: HKEY_CURRENT_USER/Software/Stellar Science/ECW Escalator/NoWarningBoxes