GIMP :: Threshold Alpha Doesn't Do Anything?
Sep 4, 2012
I want to use the Threshold Alpha command on a Layer of Solid Noise, but nothing happens. If I set the threshold to 255 everything goes transparent, anything below that the clouds are supremely unimpressed. It's an RGB image, has an alpha channel, no Alpha channel lock, the Threshold tool works fine. I also tried creating another test picture with several gradient in greys and colors, and they are equally unaffected by Threshold Alpha.
I'm using GIMP 2.6.11 on WinXP SP3.
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May 31, 2012
I am using the latest version of GIMP on my windows 7 pc but color to alpha doesn't work. At my pc at work it works fine but i use windows xp there and i have ghostscript and python installed.
Or is it something completely different?
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Jan 21, 2014
i tried restarting gimp but it did not fix my problem. All of a sudden, out of nowhere, my fuzzy select tool selects WAY too much even at a threshold of 1. at 2 it just selects the whole picture.Re-installing did not fix.
i am creating black/white based icons. So it is a 48x48 image. i am mainly trying to fuzzy select black, white, and transparent selections. As you can guess, it has become impossible now and i don't know what i did.
EDIT: Okay so it actually isn't selecting "too much" per-say. i willt ry and explain the best i can here:
Black and white image with the exception of some shades inbetween.Select fuzzy select and put threshhold at 1. Click. Selects all the white (i actually think it misses some). i hit SHIFT and click on a pixel that is slightly not white. VERY SLIGHTLY. In fact, it may actually be white. It fuzzy selects EVERYTHING.
Another example on an image that is Black and Transparent (with shades inbetween) Slect black on threshold 1. It selects All the black AND all the shades inbetween. Eveything except flat out transparent. i hit CTRL and select a shad einbetween and it deselects everything.
EDIT 2: Doesnt matter the threshold apparently. It will do this on any.
EDIT 3: The solution, after all, was so save these problematic images as JPG and then open them as the JPG.
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Apr 1, 2012
I would like to obtain a black and white image of a photograph of a book page.
My attempt to do this is by running the threshold function over theentire image. This appears to give the desired result, but onlylocally. It appears that the optimum parameters of the thresholdfunction vary by position (i.e., according to some scalar field), withone extreme in the center of the glare and then radiating outward. Sojust running the threshold function over the entire image withconstant parameters always gives sub-optimum contrast for 75% of theimage. Will I have to find a way to run the threshold function withnon-constant parameters, or is there some other tool to do the job?
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May 3, 2013
I scanned some images to Tiff format and when I bring them into Gimp I can't seem to get the threshold effect to work. The other color effects work but not threshhold. I check with other Tiff images I have and they work but not for this new set (done on a different scanner).
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Nov 24, 2008
When I use the "Save As..." command to save a picture with transparency as a Windows bitmap file (.BMP), the transparency information gets lost. I selected alpha-channels and chose 32-bit in the BMP options dialog.
In CS3 this works fine.
how I can get it to work in CS4? The target program can only read BMP-files, so my workflow depends on it.
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Sep 23, 2011
When I save a render as PNG and then open it in Photoshop, it doesn't have the alpha channel, just R,G & B channels. The PNG Configuration Setup when saving the image has of course Alpha channel box checked, but is not available when I open the file in Photoshop.
Note: I was able to do this in 2008 version.
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Aug 12, 2013
I have a 24bit PNG image to be used as a texture in my little game. I want to blend this texture with other colors which require it to have an extra alpha channel. I did some search online and tried some methods including add another layer and add transparency to the image, but neither worked(after I exported the image to png and reopened it, it still only contains 24 bits for every pixel).
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Jul 17, 2013
I'm using 2.6. How do I add an Alpha Channel?
I can't find it in the selections.
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Jul 4, 2013
When I color a the background of a photo to alpha it works just fine, I save it and export.
But when I try to open that same photo anywhere else the background is white .
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Apr 19, 2011
How to do the steps described in the article "How do I Import Alpha Textures?" (
[URL].... butwith GIMP?
Is special, how can I create an explicit alpha channel that I can manipulate?
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Dec 7, 2011
making a alpha channel transparency; Funny thing is. I made it work once a few days ago. I went to bed and forgot to write down how i did it (Tried everything, almost)
In the link right here [URL] n i have 4 files; Q3a_arrow_gimp_ver4.tga (TGA that works as i want it, you'll notice ALL the alpha channels have a black layer channel in the channels tab, how do i recreate that?) Q3a_arrow_methodtry.tga (tried to recreate with THIS tutorial [URL] with no success P.S. i tried loooads of tutorials but this recreation seems rather close to the working .TGA i need) Q3a_arrow.ai (sourcematerial all vector from Adobe Illustrator) Q3a_arrow.png (picture with transparency intact if needed for comparison)
So; Now... What i did to make the working picture was making a .PNG - drag it into gimp.. I recall doing some Alpha and or masking or selection thing with it, then rendered it for .TGA since Illustrator does not support the kind of .TGA i needed. Worked flawlessly in the engine where i use a function called alphafunc GE128 (blend with black as invisible layer and white as solid)
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Jul 12, 2013
Is there an easy way in GIMP to invert the alpha channel of an image? Transparent should be opaque, opaque should be transparent, almost transparent should be almost opaque, etc.
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Mar 21, 2012
I have a B&W images. It's actually in RGB but all shades are gray. I would like to create an alpha channel whose values equal the brightness of each pixel. How do I do that?
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Oct 14, 2013
How do I set the spacing to make this brush draw seamlessly?
Attached File(s) brush_spacing.jpg (25.86K)
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Nov 2, 2013
Some .BMP files.
I need to save some images with transparency that are in .BMP format, but said images seem to have what's called an alpha channel, which covers all of the image's background and not the transparency that I need. I've tried to use the "Convert color to alpha" option, but it appears that that only works in the image that I want and not in the alpha channel itself (yeah, I didn´t know what alpha channel was until then).
I leave an example of one of the various .BMP files that I want converted to .PNG with transparency.
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Nov 9, 2011
I'm trying to create an image which emulates a solar corona (it's basically just a blurry circle). It's as easy as making one brush stroke in gimp, but my problem is that i can't get all the channels to be correctly set.
Ultimately i just want to edit the alpha channel, NOT the RGB ones. They should all be pure white, or 255, 255, 255. But for some reason, no matter how much masking or color selection or clicking only the alpha channel and not the RGB ones or anything that i do, i cannot keep the RGB white while editing the alpha channel, every stroke that affects alpha seems to invariably affect the other three.
How can i edit ONLY the alpha channel?
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Aug 5, 2013
My task is to do a batch processing over an folder with images. I want to add an alpha layer to every image (png). The alpha layer is from a static second image (bmp).
I can accomplish the task in the GIMP front end manually, but the exactly same steps in my script aren't working.
Here's the script:
(define (script-fu-batch-alpha-add globalpha globpics) (let* ((filelist (cadr (file-glob globpics 1))) (filealpha (car(cadr (file-glob globalpha 1)))) (imgalpha (car (gimp-file-load RUN-NONINTERACTIVE
filealpha filealpha))) (drawablealpha (car (gimp-image-get-active-layer imgalpha)))
[code].......
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Jul 24, 2011
Thought I'd try Gimp on my new laptop instead of Photoshop. I'm making graphics for a game.
I needed to add an alpha channel to an image and edit it, including pasting into the alpha channel from the clipboard. Easiest thing in the world on Photoshop, but seems utterly impossible on Gimp.
I've looked at a few threads that discuss editing the alpha channel, and they make it sound like rocket science. Notable, most seem to involve juggline multiple other images and then following convoluted pasting operations to get anything down. Or using layer "Masks" which, as best I can see, are impossible to paste into (and I couldn't find how to convert these masks to alpha channels either.)
As it stands, I've failed to get anything onto an alpha channel at all, except some scribble that showed up in the tiny side icon but couldn't be seen in the main image.
I'm new to Gimp, and I'm hoping I've just missed something. What is the straight forward way to edit the alpha channel (drawing on it, pasting into it from the clipboard), and seeing the results at the same time. I've tried everything intuitive and nothing works.
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Sep 27, 2012
Is there anything that can be done using an alpha channel, that can'tbe done using masks and layers, or vice versa? Context of question: I've worked extensively with masks and layers.I've never worked with alpha channels.For example:
Using an alpha channel:
1. Open two single layer images, A and B, neither one of which has analpha channel.
2. Drag the image B over to A and close B.3. Now image A has two layers, A and B. Put layer A on top, selectlayer A, set the blend mode to Normal, and add an alpha channel.4. Erase part of layer A, where-ever you want layer B to show through.At this point, layer A has an alpha channel with white where you wantlayer A to show, and black where you want layer B to show, but it doesnot have a mask.
OR
Using a layer mask:
1. Open two single layer images, A and B, neither one of which has analpha channel.
2. Drag image B over to A and close B.3. Now image A has two layers, A and B. Put layer A on top, selectlayer A, and set the blend mode to Normal (don't add an alphachannel).
4. Create a solid white mask for layer A. Paint black on the maskwhere you want layer B to show through.At this point, layer A has a mask with white where you want layer A toshow, and black where you want layer B to show., but it does not havean alpha channel.
In both cases, using a mask or using an alpha channel, the net resultis the same.So again, is there anything that can be done using an alpha channel,that can't be done using masks and layers, or vice versa?
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Mar 7, 2013
My link but when I get to the part where it says to add the alpha channel - add alpha channel is greyed out in gimp.
I'm using Gimp 2.6 - windows xp.
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Mar 21, 2012
Is it possible to directly edit the alpha channel? I need to edit it for a 3D model I've made, and its showing up as too shiney (The engine is looking at the alpha for reflectivity).
However, I have yet to see a way to edit the alpha channel directly.
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Sep 13, 2012
I had a .JPEG of a leaf photographed against a white background. When I went to turn that white background into a transparent alpha channel, it seemed to work okay....except for the fact that when I then went to select the new alpha channel via the Fuzzy Select Tool, it wasn't selecting all these newly transparent pixels.
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Feb 26, 2013
Basically I need to be able to add different information into each channel including the alpha without the image being transparent at all.
Not to compare at all, but in photoshop i could work solely in the alpha channel without the RGB channels visible, then enabling the RGB channels would allow me to see the entire image without any transparency.
Basically, i want to be able to use the alpha channel for things other than transparency. For storing different masks in each channel for use in shaders.
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Mar 8, 2013
I know how to add alpha channel to each layer individually and manually but is there a way to have an alpha channel added to each new layer automatically?
I'm using 2.8.2
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Dec 18, 2013
I started using gimp yesterday to remove backgrounds out of images for my website so have done it fine.
But now I clicked on something which reduced the toolbox dialog box to not be as large - ie it does not show you pixels size etc if you select pencil tool now.
Also I open an image and lasso it - then click the quick mask but the pencil tool is not adding any more to the area - it wont draw over or anything. The lock alpha button is on in the layers panel and I cant unlock it.
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Jul 27, 2011
I have an existing (grayscale) image that I want to make into the alpha channel for another image.
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Mar 9, 2012
I don't understand how you can know which colors to use when applying "Alpha to Color".
Here are a few images I have and what I've done so far:
Here are my original images
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Nov 25, 2012
Basically, I am trying to use an alpha layer/channel to export a picture that is transparent except for a grass clump that is colored green over the alpha layer. So the picture looks like a solid green rectangle, but is actually a green blade of grass.
Problem is, I cannot get the alpha layer to work. I can't follow the tutorial as it is in photoshop, and random videos on-line haven't worked.
(Here is the tutorial: [URL]...... from 08:40 - 09:30)
(I have also attached my practice file as a TGA)
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Oct 26, 2012
I have been doing light box photography, but I want to get that pure white background as product images usually have.
My background is a light grey.. Using the wand tool, I was able to get close - but far from close enough.
[URL].....
What's the right method, to turn every thing around the dime, white?
Here it is before the wand,
[URL]......
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Jul 22, 2013
1.I am working on a project where I need to set all pixels below a level as alpha channel, is there a quick way to achieve this? The level can be both set a prior or adjusted dynamically, the second way is preferred. Right now my workflow includes:1. duplicate layer.
2. use color level in duplicate layer, in menu COLOR -> LEVEL.
3. add alpha mask to original layer
4. copy duplicate layer into the alpha mask of the original.
5. delete duplicate layer.
6. If result is not ok then return to 1.As you can see this workflow is a headache, specially point 6 which is often achieved.
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