font and bitmap loading is slow

GTT TFT Support

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font and bitmap loading is slow

Post by dirac » Fri Dec 28, 2012 8:01 am

I have a few concerns with the GTT display.

My first problem is the extremely slow time required to display fonts. On my unit, it's terrible. I know it's not a programming error on my end, because it's the same speed when I display text in the Autoexec file...
It takes a few seconds to display a single line of characters in the standard system font. I have the same problem when I use a different font. I know I can use Manual Updates to render the screen all at once, but the slow rendering of fonts is still a problem for the execution speed of my program...

My other issue is with loading bitmap file. I have a virtual keyboard made up of 28 images times 2 (up/down version of each one). It works fine, but the loading time is very slow. I use 39x39 pixels BMP with 256 colors... Is there a better file format to reduce loading time ?

Finally, I would like to make a suggestion for the next hardware revision of the GTT. You should change the resistive screen for a capacitive one.

(For the records, I upgraded my unit to the last firmware revision...)

Matrix Orbital
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Re: font and bitmap loading is slow

Post by Clark » Fri Jan 04, 2013 11:03 am

Hi Dirac,

Experimentally, using the default font, I have measured the GTT write speed for a single line of text as approximately 1 second. I understand that this will be visually noticeable when writing large text strings to the unit. Where possible I would recommend creating smaller regions of dynamic text to reduce drawing time or using a bitmap to move the delay from drawing to loading.

Full colour bitmaps will require time to load, but will draw quite quickly. I would recommend loading all required images when the unit boots. Also, you might find that the compression of a .gif file will create a file that is smaller and faster to load.

Finally, while we are changing a number of things on the next GTT revision, including speed, the touch screen will remain resistive. Currently, the largest market for these units is more industrial rather than consumer, so resistive touch will continue to be the default interface because it is more robust in electrically noisy environments and can be used with standard gloves. Capacitive touch will remain a custom option for any larger projects where it may be required.

Troy Clark
Design & Development
Matrix Orbital

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