Why is RF Plan unable to display a JPEG background image with progressive compression?
Product and Software: This article applies to RFPlan in the WebUI of all ArubaOS versions.
JPEG images with progressive compression cannot be used as background image in RFPlan in WebUI.
The Adobe Flash Player is used in the RFPlan of the ArubaOS WebUI to display floor plans. However, the Adobe Flash Player does not have a decompressor for progressive JPEG images. Therefore, these type of images cannot be used as background images in RFPlan. For details, see the KB article from Adobe at this URL:
To mitigate this problem, open the image in an image editing program such as Photoshop and resave the image with standard/baseline compression. This screen shot is from Adobe Photoshop:
Baseline JPEG vs. Progressive JPEG
JPEG come in two flavors: baseline and progressive. Baseline JPEG is an image created using the JPEG compression algorithm that will start to display the image as the data is made available, line by line. In a web browser, you can see JPEG images that are in baseline format when you see it slowly showing up, from the top of the image, to the bottom of it.
Progressive JPEG displays an image in such a way that it shows a blurry/low-quality photo in its entirety, and then becomes clearer as the image's data becomes more fully downloaded.
Progressive is good because the user gets an idea of what the image will be right from the start, even though it's not as clear as the final image, which is great especially for people with slower Internet connections. The progressive JPEG format also enhances perceived web page performance because it doesn't appear to be loading in increments, unlike baseline.
JPEG Baseline/Progressive Format in Photoshop
When you use Photoshop's Save As feature (File > Save As) to output your work in JPEG format, you will be presented with the following Format Options:
- Baseline: The image will be displayed line by line on the screen.
- Baseline Optimized: Same as Baseline, but optimized further using Huffman coding.
- Progressive: You can specify 3-5 scans, meaning that it will have between 3-5 phases before it shows the final image.