STM CircleOS forum / Jpeg to BMP

Francis · 2009-10-14 15:52:51

We are working on a new Primer, that will have a 320 X 240 LCD.
Until now, we used to save the images as bitmap. It was ok for the icons, but it was an issue for the image of the 'home page' (approximately 128KB). With the future LCD, the size of the images will be approx. 4 times bigger. That's by far too much for the available FLASH...
Does anyone know where to find an efficient 'jpeg to bmp', open source converter that could be easily embedded into CircleOS ?
Thanks for your help.

sjoerd · 2009-10-18 09:00:50

you can have a look at:

http://sourceforge.net/projects/mb-jpeg/
http://www.saillard.org/programs_and_pa … egdecoder/
http://www.stud.fit.vutbr.cz/~xpolok00/ … iso-8859-2 (c++)

Perhaps PNG could also be considered because decoding is a easier

Francis · 2009-10-19 10:33:02

Thanks for the links. Did you try to implement one of these algorithm on a Primer ?

Francis · 2009-10-19 12:40:01

It seems that all algorithms require too much RAM...At least the image size (*2 for colour). Not possible on Primer1/2.

basic · 2009-10-23 08:58:09

Hi, I'm new here. And have just a few hours experience in practical STM32-programming. So go easy on me. :-)

A quick look tells me that the first link above does BMP=>JPG only, not the other way. (Did I glance too quickly?)

The second one seems pretty simple to modify so that it calls a function provided by the user for every decoded JPG block (max 16x16 pixel). If that function sends the block directly to the LCD, you'll only need a 16x16 frame buffer in the STM32.

Maybe I'll look into such a mod this weekend.

But beware, that code includes a bunch of floating point calc in the inner loop. I don't know how well that will work on the STM32.

yrt · 2009-10-23 10:07:46

Effectively it uses float variables for the DCT (Discrete Cosine Transform), and it will not do it with CircleOS !
But it seems that it would be possible to replace this function by another one with integer calculation (see the libjpeg site, it exists several versions).

# 1 2009-10-14 15:52:51 Jpeg to BMP

Jpeg to BMP

# 2 2009-10-18 09:00:50 Jpeg to BMP

Re: Jpeg to BMP

# 3 2009-10-19 10:33:02 Jpeg to BMP

Re: Jpeg to BMP

# 4 2009-10-19 12:40:01 Jpeg to BMP

Re: Jpeg to BMP

# 5 2009-10-23 08:58:09 Jpeg to BMP

Re: Jpeg to BMP

# 6 2009-10-23 10:07:46 Jpeg to BMP

Re: Jpeg to BMP

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