[FFmpeg-user] How to make partially transparent png image

[qw]

I have one question about alpha channel and transparent background in png file.


Png file supports alpha channel, which controls the transparency of pixels. If there is transparent background in png file, I can see the pixels of the bottom layer from overlayed image.


Does transparent background has pixels and alpha value in png file? For example, transparent background has any value of rgb, and its alpha is set to the value associated with full transparency. Is that right?








At 2015-06-29 00:27:02, compname at verizon.net wrote:
>At 6/28/2015 02:09 AM, you wrote:
>
>> > Since ffmpeg is a video processing tool, even if it could I wouldn't
>>recommend it.  I used another free tool: IrfanView.  I believe you can load
>>an image into it & tell it to make a certain color/range of colors
>>transparent.
>>
>>IrfanView is not free
>
>Well, OK for commercial use it's not free.  But just about any 
>business (that's planning on staying in business anyway) isn't going 
>to quibble over the $12 reg. fee.  And for us 
>individuals/educators/etc. it is free.
>
>>  and ffmpeg have already tools to make certain
>>color/range of colors transparent.
>
>I've recently used the geq filter to do just that.  But I never 
>considered FFmpeg to be a (still) image editor/converter, even though 
>it does work nicely as such (-i in.bmp -vf [image filters] -c:v png out.png). 
>
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