Thursday, June 19, 2008

Dithering Images for Mobile Devices

I wanted to share some of my experiences creating images on mobile devices. My experience in this respect is specific to Windows Mobile, however this will likely transfer to other types of smarpthones or handheld devices.

First a little background on colors and our ability to perceive them (this is relevant). Scientists believe we're able to distinguish roughly 10 million different colors/shades. So computer scientists have decided that displaying colors from a possible selection of about 16.7 million colors should cover what we can see. This is known as 24 bit color - or TrueColor. In 24 bit color, we use 8 bits of information for Red, 8 for Green and 8 for Blue. 8 Bits gives us a range of values from 0-255. So as you can now work out - we have 256 possible values for each color - and 256x256x256 gives us about 16.7 million.

Now on mobile devices, where memory is limited and screen sizes are small anyways - most modern smartphones use 16 bit color screens instead. On 16 bit devices you get 5 bits for Red, 6 bits for Green and 5 bit for Blue again. So our total number of colors is 32x64x32, which equals 65536. And on a small screen this gives us a pretty good looking image in most cases.

Where you run into trouble is with images that consist mostly or entirely of one color - for example - a gradient that goes from Black to Blue. In this case, we will not be using Red or Green at any point in the image, so we can only differentiate the color by changing the Blue level. With 5 bits we get 32 steps, so if we draw the gradient mentioned above, you will be able to see 32 bands of color and at 16 bit there is no way to get additional shades of Blue.

This is an excellent example of where dithering can be useful. Dithering, simply put, is the act of adding noise or errors. As it relates to images, this noise can be done in such a way that it will fool the eye into thinking there are more colors present.

Now at this point if you'd like further clarification there is a wealth of information online discussing this in further detail: a simple Google search will do nicely.

I would like to focus on the practical aspects. So back to creating mobile software, if you're creating graphics on a desktop machine I would recommend first creating all of your images as 24 bit graphics and then using software to dither to 16 bit. My favourite application for dithering is ACDSee Pro 2.

This will accomplish three things:
1. Your images will be dithered so they will look as good as possible on a 16 bit screen
2. Your images take up less disk space (50% smaller in the case of bitmaps)
3. Your images will load faster as the device isn't required to convert from 24 to 16 bits when displaying (on Windows Mobile devices there is a performance penalty for this)

Now onto the really interesting part, if you create any graphics in code, ie, dynamically generate gradients, controls, etc. You can still dither from 24 bit to 16 bit.
You'll need to create a 24 bit memory buffer, render to the 24 bit buffer using full 24 bit values.

Now you'll create a second 24 bit buffer to copy the dithered version using your algorithm of choice. Once you've copied this over you'll then want to copy the dithered information to a 16 bit buffer. This is easier than it sounds as all of your 24 bit values with be "16 bit friendly".

My favourite dithering algorithm is the standard Floyd-Stienberg and Wikipedia has a great write-up containing pseudo code:

This code is trivial to convert to C++ but note you'll need to dither each color individually (Red, Green, Blue) and your errors will need to be calculated individually as well.

And of course you'll need to keep an eye on the edges, you can simply indent by one pixel all around when dithering. In "most" cases this won't affect your results.

Please feel free to write if you have any questions or comments.

Arkon Universal PDA Mounting Kit

As the title suggests I recently ordered an Arkon Universal PDA Mounting Kit after a recommendation from a user on

My mounting kit arrived yesterday and I have to admit I'm impressed. The Universal has three mounting options however one doesn't really count as it involves placing a plastic disc on your dash using the supplied adhesive.

The other options are a windshield mount and a vent mount. I assumed I'd simply use the windshield mount as its quite solid and its the mount of choice for most GPS devices. However, the vent mount is really easy to install/remove and its in a perfect position in my Acura CL.

The only signifigant draw back to this solution is the lack of a power cable. Fortunately, I already had a car charger that was included with one of my past cell phone purchases so this wasn't a concern.

I'm currently using the mount with an iMate JAQ3 and a Toshiba G900 - both of which sit very securely. I also briefly tested the mount with three other phones: The HTC Touch and the Motorola Q should work very well. The mount is too wide to grip narrow phones like the T-Mobile SDA (iMate SP5).

Arkon Homepage:

Wednesday, June 18, 2008

Employees and Time Management for small companies

I wanted to write a little about hiring employees, and specifically how to save time and hopefully a little money.

I think we all know that when you're growing or running a small company you end up doing a little bit of everything. And when its a high tech company you're often divided between the mundane tasks that you have to do and the skilled work you need to do to keep your business running. To offload some of the work we hire software developers but taking time to manage and train means I personally get less work done.

So my business partner and I realized we could get ahead by hiring employees to do the non high-tech work.

One of the best things we did for our small software company was to hire a cleaning staff - both for the office and the home. As I know my business inside and out - I'm probably as valuable as 2-3 new hires - so freeing up a few extra hours a week to work on the business is almost like hiring another part time employee. And having a cleaning staff come in shouldn't cost much more than $100 per visit. As a company we spend less than $500 a month to keep our homes and offices clean.

This is an easy way to increase productivity without HR headaches - and this way I don't have to take out the garbage.