[fpc-pascal] Questions regarding FPImage's TFPMemoryImage.FData variable

[Graeme Geldenhuys]

On 2016-05-26 12:08, Michael Van Canneyt wrote:
> BUT: 
> depending on UsePalette, it contains indexes in the palette or RGB Data.

Oh, I forgot about Palette usage. I’ll have to check for that in my
code. Does setting UsePalette := False at runtime auto convert palette
data to RGB data? I had a look at TFPCustomImage.SetUsePalette() but it
is not immediately obvious what it does at runtime (after image data was
already loaded).


> It is definitely possible that you are wrong. 

:-) Definitely not the first time that happened.



> Yes. The Pixels array is a palette. The colors array is RGBA.

Good to know the difference, thanks.


>> 4) What is the order in which the colour channel information is stored
>>   in memory? RGB, BGR, RGBA, BGRA, ARGB, ABGR etc?
> 
> You should not worry about this. The whole idea is that you do not use the
> internal format, but just use the colors array:

But that would be super slow.


>> The reason for all these questions. I've got a image loaded in a
>> TFPMemoryImage instance. I need to pass the the raw pixel data buffer to
>> a 3rd party library for further processing. But I need to tell that
>> 3rd party library a bit about the data I'm giving it (colour channel
>> size, colour channel order etc).
> 
> This is not supported for TFPMemoryImage.

Well, I seem to have it almost working (see my other message with
attached image). I didn’t know about the TFPCompactImgBase descendants -
I’ll give them a try instead. That seems more like what I need.

Many thanks for all the information Michael.


Regards,
  Graeme

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