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 Post subject: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 3:46 pm  (#1) 
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So does BMP Support Transparency? Does anyone know this, I have looked on a few articles and it starts talking about Vector saving versus Bitmap saving, and well that is just a bit deep for a Tuesday Afternoon.

So does BMP support Transparency and if not then what is a good alternative?

I am looking for an image that can be re-sized, proportionaly of course, and not lose quality, and I had a friend tell me BMP is what I am looking for.

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Willy

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:07 pm  (#2) 
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No only gif and png support transparency.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:08 pm  (#3) 
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Well then, nothing else does? And is Bitmap at least good for the Resizing without Quality loss?

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:16 pm  (#4) 
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Your friend is talking though his hat :) BMP is a bitmap format, just like PNG. If fact in some cases its content can use the JPEG or PNG formats. If you want rescaling without losing quality (for computer graphics, not photographs) then you need a vector format such as SVG.

Vectors format inherently support transparency, where they don't draw there is nothing...

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:18 pm  (#5) 
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So to be correct, Vector does support transparency and for resizing without Quality loss I should use SVG?

Does GIMP support SVG?

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:22 pm  (#6) 
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yes

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:25 pm  (#7) 
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Thank you guys for the help. I never would have figured this out on my own.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 4:26 pm  (#8) 
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You are welcome Willy anytime. :)

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 5:55 pm  (#9) 
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Rod wrote:
yes
To be accurate: you can load an SVG file as an image (you get to choose the size in pixels) or as a path (as far as I know) and you can save a path as SVG (again, as far as I know, I have not experimented with that) but you cannot save an image as SVG. If you want to create SVG, the proper tool is InkScape.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:08 pm  (#10) 
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So to be correct, My question still does not have an answer...

Is there a format for images that does not lose quality when Re-sized?

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:16 pm  (#11) 
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You can now export files as SVG using GIMP and a plug-in.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:17 pm  (#12) 
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Then, when you go to open it, you can re-size to whatever you want and it will not lose quality?
That is all I am looking for, is just the ability to re-size without quality loss, if this is even possible.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:26 pm  (#13) 
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@Willy

The short answer for bitmap images is no, because a bitmap image consist of a two-dimensional grid of pixels and reducing the size means to throw some of those pixels away and interpolating between them in some way. So a bitmap image can never be resized perfectly loss-less per definition. The rescaling can be very good though, so good that you won't notice degrading unless you get down to very small sizes.

The best format for saving an image in optimal quality is PNG (this also supports transparency). JPG/JPEG usually takes less space than PNG but does not support transparency and saves space at the cost of quality. GIF handles transparency and simple animations, but is limited to 256 colours. If you work in GIMP, you should work in XCF (which is GIMP's internal format, supporting layers etc) all the time, only doing "Save a Copy" to PNG or JPG when you want to put your stuff on the web.

As others have mentioned, a vector image can be rescaled without loss of quality, but that is because a vector image (as created by e.g. Inkscape) is not made out of a two-dimensional grid of pixels but of mathematical functions - creating a vector image is a quite different process from the work process of bitmap editors like GIMP or MyPaint. As said, GIMP can import a vector image in SVG format. but only in order to convert it to a bitmap - from there on it works like above.
.
Griatch

PS: Mahvin: Is that a path-based tool, or an actual bitmap->vector conversion?

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:28 pm  (#14) 
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Thanks for the answer, I should have said I already have a basic understanding of GIMP... So I know what PNG, and XCF, and JPG, and GIF are, but the Vectors are confusing, but I think I understand now,

GIMP cannot save images as a Vector right?

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:31 pm  (#15) 
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Willy wrote:
Thanks for the answer, I should have said I already have a basic understanding of GIMP... So I know what PNG, and XCF, and JPG, and GIF are, but the Vectors are confusing, but I think I understand now,

GIMP cannot save images as a Vector right?

That is correct. GIMP is a bitmap program. It can load a SVG vector image from e.g. Inkscape and convert it to a bitmap, but from there on it works like any bitmap image and will be saved as such. Vector image creation is quite a different from how GIMP works.
.
Griatch

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:32 pm  (#16) 
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Thanks for the information, this kinda stinks... Thanks for all the help guys,
I really appreciate it.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:34 pm  (#17) 
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Cubic or Lanczos3 scaling interpolations work very well in GIMP, what is it you are doing that requires pixel-by-pixel perfect rescaling?
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Griatch

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:37 pm  (#18) 
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Not exactly perfect, but we are making a Soda Pop (kinda corny), for school, and we have to make a Logo, and I have no idea what the size is gonna be, because we can't decide on whether we are going to use a Can or Bottle, and then 20 or 12 oz Can or some two sizes of Bottles... So yeah... it would be nice if it didn't have to be remade each time.

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 6:42 pm  (#19) 
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Seriously, for a logo you'd probably want to use vector graphics anyway ...

If you want to do it in bitmap graphics, make sure to make it large from the onset (pick at least a 300DPI resolution); shrinking it down is always better than scaling it up.

Hm, I just noticed above that Mahvin said there is a plugin for saving into SVG from GIMP. Haven't used that.
I do know that Inkscape can convert a Bitmap image into vector though. The result is not quite the same as the original (depends on how many colour gradients you use), but I have used it to create logos myself a few times (then you need to work in Inkscape rather than GIMP though).

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Griatch

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 Post subject: Re: Does BMP Support Transparency?
PostPosted: Tue Mar 08, 2011 7:27 pm  (#20) 
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Well there is a bmp with alpha option (i.e., 32-bit image) but I'm not sure if many viewers support this. Irfanview just looks at the transparent color and views it flatten, but this one will open in GIMP with the embedded transparent alpha. It's 1.7MByte and just an excercise so go ahead and open it up in GIMP. :)


Attachments:
go.zip [1.38 MiB]
Downloaded 159 times

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