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Alpha transparency space in borders for stickers. - Printable Version

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Alpha transparency space in borders for stickers. - Tetragram - 01-01-2019

Hey Guys. I'm creating stickers, and I want to send to the printer, information that there's a couple of inches of transparency after the edge of the images. I'm making it about 2 to 4 pixels. Something small.

I have the cut out in Gimp, but can't figure out how to do that. 

I have read about the tools and searched the web as well but haven't found an answer. 

Any help is appreciated.


RE: Alpha transparency space in borders for stickers. - Blighty - 01-02-2019

Sorry, from the description I am not understanding the problem.

Is there transparency that needs to removed, or are you wanting to add transparency?

Is the size a couple of inches or 2 to 4 pixels?

Could you attach an example image that shows the problem?


RE: Alpha transparency space in borders for stickers. - Tetragram - 01-02-2019

(01-02-2019, 06:34 AM)Blighty Wrote: Sorry, from the description I am not understanding the problem.

Is there transparency that needs to removed, or are you wanting to add transparency?

Is the size a couple of inches or 2 to 4 pixels?

Could you attach an example image that shows the problem?

Probably 2 to 4 pixels in most stickers, if it is needed I'll add more pixels. 

If I start doing XL size stickers maybe I have to add inches. For now pixels.

Right now, the image is cut at the black border. If I send it like that, the sticker starts at the border. 

I want to add, to the border, an amount of transparency (varying on the sticker and sticker size), so instead of being the border of the sticker the border of the image itself, it has an amount of transparency with the same shape of the border, being that the border of the sticker then. An outline of transparency with the shape of the image.

So for instance, if I use fuzzy select and outline the contours, then I'll use >select>grow> 4 inches, that space, between the black border and the selected zone, is the one I want to be transparent and be in the image.

This render has a back color so you can see the borders, the image is only the skull. 

[Image: 3VzZ96r.png?1]


RE: Alpha transparency space in borders for stickers. - Blighty - 01-02-2019

If I understand correctly:
You start off with the image below and want to add 4 pixels of transparency all around.

Do Image > Canvas Size. Add 8 pixels to the width, 8 pixels to the height, and use the Center option. Complete by using the Resize button.


RE: Alpha transparency space in borders for stickers. - techie1484 - 01-02-2019

(01-02-2019, 04:40 PM)Tetragram Wrote: So for instance, if I use fuzzy select and outline the contours, then I'll use >select>grow> 4 inches, that space, between the black border and the selected zone, is the one I want to be transparent and be in the image.

This render has a back color so you can see the borders, the image is only the skull. 

[Image: 3VzZ96r.png?1]

So I understand that the requirement is for the blue border around the skull to be trasnparent yet still preserve both background and skull colors.

I assume you have a separate file of the background and skull.

To achieve this,First both background and skull image needs to be merged into a single layer and saved as a seperate file.

Then open the file using file->open as layers.

Then right click on the layer thumbnail on the layers dialog,select "add layer mask" and choose "white(full opacity)".

Make the same selection on the skull as done earlier and perform select->grow->(required border dimensions)

Fill the foreground color with black(which will mark a transparent layer including the skull and the border).

Perform file -> open as layers - choose the file only with the skull.

Then we would require relative positioning of the skull to fit exactly in the transparent region created through the layer mask in previous step.

To achieve this,

1) use move tool.But use arrow keys instead of mouse(without click and drag).Hold shift and arrow key to move 25 pixels in the right direction and only arrow keys to move pixel by pixel.If you get the position pixel perfect to even one of the edges in the skull,the rest will align themselves as the transparent region contour is the same as the skull.

2)If the selection of the skull area is possible on the mask(without the select -> grow step) which contours only the skull. Then make the selection on the mask. Since the skull image is in a seperate file with contour of jus the skull.Perform File -> Open.Open the file with contour jus with the skull. Perform Edit -> Copy. Then select the current file which has the layer mask with transparent region.Perform Edit -> Paste in selection.

Current file will have background,layer mask and a layer with only the skull.

Any option to merge all of above final layers output to single layer should give the desired result.


RE: Alpha transparency space in borders for stickers. - Tetragram - 01-02-2019

(01-02-2019, 06:27 PM)Blighty Wrote: If I understand correctly:
You start off with the image below and want to add 4 pixels of transparency all around.

Do Image > Canvas Size. Add 8 pixels to the width, 8 pixels to the height, and use the Center option. Complete by using the Resize button.

Thanks. I think that would do exactly what I'm looking after.

So instead of having the image cropped at the edge, at the black outline, doing what you mentioned, would create, where the magenta outline is in the second image, a "space" filled with transparent information in the .PNG file, an outline of alpha transparent channel so the printer reads it as is and creates a sticker with those characteristics. Did we hit the bullseye?



[Image: JVqwcm1.png]




[Image: b2xvq8A.png]

(01-02-2019, 06:36 PM)techie1484 Wrote:
(01-02-2019, 04:40 PM)Tetragram Wrote: So for instance, if I use fuzzy select and outline the contours, then I'll use >select>grow> 4 inches, that space, between the black border and the selected zone, is the one I want to be transparent and be in the image.

This render has a back color so you can see the borders, the image is only the skull. 

[Image: 3VzZ96r.png?1]

So I understand that the requirement is for the blue border around the skull to be trasnparent yet still preserve both background and skull colors.

I assume you have a separate file of the background and skull.

To achieve this,First both background and skull image needs to be merged into a single layer and saved as a seperate file.

Then open the file using file->open as layers.

Then right click on the layer thumbnail on the layers dialog,select "add layer mask" and choose "white(full opacity)".

Make the same selection on the skull as done earlier and perform select->grow->(required border dimensions)

Fill the foreground color with black(which will mark a transparent layer including the skull and the border).

Perform file -> open as layers - choose the file only with the skull.

Then we would require relative positioning of the skull to fit exactly in the transparent region created through the layer mask in previous step.

To achieve this,

1) use move tool.But use arrow keys instead of mouse(without click and drag).Hold shift and arrow key to move 25 pixels in the right direction and only arrow keys to move pixel by pixel.If you get the position pixel perfect to even one of the edges in the skull,the rest will align themselves as the transparent region contour is the same as the skull.

2)If the selection of the skull area is possible on the mask(without the select -> grow step) which contours only the skull. Then make the selection on the mask. Since the skull image is in a seperate file with contour of jus the skull.Perform File -> Open.Open the file with contour jus with the skull. Perform Edit -> Copy. Then select the current file which has the layer mask with transparent region.Perform Edit -> Paste in selection.

Current file will have background,layer mask and a layer with only the skull.

Any option to merge all of above final layers output to single layer should give the desired result.

Thanks for the reply, but the background was to show with precision where the outline was, the bluish border was something that remained from my previous try outs of adding an alpha outline. Anyways your concept is very interesting, I might apply it to further works.

I think that following the process that Blightly explained I can achieve an alpha transparent outline. I'm waiting for his confirmation, so we know we both are speaking about the same thing.


RE: Alpha transparency space in borders for stickers. - rich2005 - 01-02-2019

In most commercial printing White = Transparency. Offset (& Inkjet) printing uses cyan, magenta, yellow, black inks mixed to create the colors. Anything White is not printed and takes the colour of the printed-on material.

You should also check the printing resolution of your image. 96 pixels-per-inch (ppi). Very low for quality printing. 200 to 300 ppi is more usual.

The usual advice. Speak to the printing company about your requirements.


RE: Alpha transparency space in borders for stickers. - Blighty - 01-02-2019

A bitmap image is always rectangular. So you cannot just add an alpha outline. Adding the 8 pixels to the width and height is the correct method.


RE: Alpha transparency space in borders for stickers. - Tetragram - 01-02-2019

(01-02-2019, 07:18 PM)rich2005 Wrote: In most commercial printing White = Transparency. Offset (& Inkjet) printing uses cyan, magenta, yellow, black inks mixed to create the colors. Anything White is not printed and takes the colour of the printed-on material.

You should also check the printing resolution of your image. 96 pixels-per-inch (ppi). Very low for quality printing. 200 to 300 ppi is more usual.

The usual advice. Speak to the printing company about your requirements.

I'm uploading my work to Redbubble, and apart from saying:

"the best resolution A good rule of thumb is that big, high-resolution files make the best prints. Now when we say ‘big’, we're really referring to resolution, not the file’s size."

and 

"If you'd like to use a single image file for every product, we'd recommend starting with 7632x6480 pixels"

"please also so note that DPI and PPI don’t have any effect on your final uploaded image."

They don't say much.

https://help.redbubble.com/hc/en-us/articles/202270679#color

They do mention that they print in CMYK and that is best to work in that format, but I couldn't get one of the plugins that does that to work in Gimp. I'm sure I'll try again in upcoming weeks when I have less work.

Also, I'm using the maximum resolution Gimp supports, which is "1048576.000" pixels/inch, and using >precision> 32 bit floating point, and exporting in NoHalo which i read that's best for up sizing images. I also read several times, that for printing, minimum for small formats is 30.000 pixels/inch. I've being meaning to get more info on that subject, but I have a rather large list of subjects which I'm going through.

I'm guessing Redbubble uses industrial professional printers for all their products. I've been educating myself on how professional printers and all that system works. But again, I'm doing 10 things at a time. 

Summarizing, Redbubble gives very little information on how to work with their platform in terms of dimensions and formats, but it's very easy to use, and they have tons of products in which you can print on. I started only 2 months ago to work with that platform and to inform myself on how to deliver the best products I can.


(01-02-2019, 07:28 PM)Blighty Wrote: A bitmap image is always rectangular. So you cannot just add an alpha outline. Adding the 8 pixels to the width and height is the correct method.

Thanks Blighty, I'll apply that method from now on when I need an alpha outline in one of my stickers, like the one I'm working on today.


RE: Alpha transparency space in borders for stickers. - rich2005 - 01-02-2019

Screwed up company Wink

The page for information is https://blog.redbubble.com/2015/10/medium-large-and-extra-large-sticker-sizes/

But then it says (for example) 3" x 4" = 450 x 600 pix and Files should be PNG with resolution of 200 ppi (DPI)
Which of course for 3" x 4" is 600 pix x 800 pix.

For a small sticker, your image 'as-is' is ok except needs the canvas sizing to 600 x 800 pix and the drawing moving slightly to the center. There is enough room there for the 1/8" border. something like this:

[Image: G4k7fkM.png]

Since this die cut vinyl & the printer adds the border, the sticker on a background would look like this.

[Image: wsIWoSN.jpg]

Keep with RGB, that is what the printing company wants. If you ever do need a CMYK image out of Gimp 2.10 see
https://www.gimp-forum.net/Thread-CMYK-color-mode-Gimp-2-10?pid=11743#pid11743