Super User
Super User

Questions tagged [alpha-channel]

35 questions
47
votes
1 answer

get pixel alpha value

Given a pixel in an image imported from a png file, how can I get the alpha value of the pixel with the GIMP? If this is not possible, what software can I use to achieve this (OS: Linux)?
greg0ire
  • 1,345
14
votes
9 answers

Extracting the layer transparency into an editable layer mask in Photoshop

Is there any simple way to extract the "baked in" transparency in a layer and turn it into a layer mask in Photoshop? To take a simple example: Let's say that I paint a few strokes with a semi-transparent brush, or paste in a .png-file with an alpha…
last-child
  • 145
13
votes
3 answers

Turn grayscale into alpha channel in Paint.net

I have a PNG image that has many shades of gray and no transparency: I would like to turn the grayscale into an alpha channel in Paint.net, so that the parts that are completely white would become completely transparent, the parts that are…
Donald Duck is with Ukraine
  • 2,629
11
votes
1 answer

How do I add a background to a transparent png in gimp?

I have a png file with a transparent background. I would like to add a non-transparent background from a jpg. I have tried: Open the transparent png file. I see the picture with the checkerboard background. Open As Layers the non-transparent jpg…
Ellen Spertus
  • 299
8
votes
3 answers

Point sample opacity/alpha in Adobe Photoshop?

I opened a PNG containing an alpha channel in Photoshop and wanted to get the opacity / alpha of a given point in the PNG file, so that I could match that opacity in a new photoshop layer. How can I do this? is there any way to get an alpha value at…
Josh
  • 9,947
7
votes
6 answers

Is there any way to save a PNG-8 file with Alpha Transparency in Photoshop?

I recently discovered something that I previous thought was impossible: PNG-8 files can store Alpha Transparency in the same way as PNG-32 files can. Not Indexed Transparency (like GIFs), but full on Alpha Transparency. (You can learn more about…
Django Reinhardt
  • 4,454
6
votes
1 answer

ffmpeg: change alpha channel of a showwaves filter

I've been trying to figure this issue out for a few hours and I can't seem to find any solution. I'm creating a video from an .mp3 and some images with the following command fmpeg.exe -y -i temp\audio.mp3 -loop 1 -i Bokeh\frame-%03d.png -r 25…
Znuff
  • 151
3
votes
1 answer

overlay a sample video with alpha channel over another video in gstreamer

I want to play 2 video files using a GStreamer pipeline on my screen. The first video is without an embedded alpha channel and I want the second video with an embedded alpha channel to be overlaid over the first one. The alpha plugin seems to be for…
nponeccop
  • 249
3
votes
1 answer

Lossless VP9 Webm Encoding of PNG Sequence with Alpha in FFmpeg

I'm trying to encode a sequence of 32-bit 8bpc PNG images (RGB with an alpha channel) using the lossless VP9 codec with ffmpeg; specifically: ffmpeg -framerate 60 -i out%04d.png -c:v libvpx-vp9 -lossless 1 -pix_fmt yuva420p output.webm This seems to…
EllipticalInitial
  • 1,800
3
votes
1 answer

Lossless Video Codec supporting Alpha Channels

Suppose I have a sequence of PNG image files which may or may not contain an alpha channel (assume those that do have an alpha channel actually utilize it). While PNG files themselves have their own lossless compression, I can usually get much…
EllipticalInitial
  • 1,800
2
votes
1 answer

How do i convert a transparent .mov-file to an mp4 file overlayed on a background-image using FFMPEG

I'm trying to convert a mov file with the following specs: Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mov': Metadata: major_brand : qt minor_version : 537199360 compatible_brands: qt creation_time : 2012-10-09…
Ernie
  • 143
  • 1
  • 8
2
votes
1 answer

How to combine multiple similar images with "holes" into one good one?

Suppose you have multiple photos of the same object (from slightly different angles), each have some obstacles in foreground. You added an alpha channel to each picture and "erased" the obstacle (leaving "holes" in each picture). You want to…
Vi.
  • 17,755
2
votes
1 answer

Keep alpha transparency in indexed PNG from Fireworks when batch resizing using convert (ImageMagick)

I have a special case where I'm using alpha transparency in indexed PNGs from Fireworks to keep the file size of PNG's in an iOS game down. (That is, indexed colors like an 8bit PNG but alpha transparency channel like 24bit PNG, yes it works on iOS…
Maciej Swic
  • 820
2
votes
1 answer

Is it possible to compress alpha and RGB channels of PNG sequence separately with FFmpeg?

Suppose I have a sequence of 32-bit (RGBa) PNG files. Is it possible to compress the RGB channel with one codec and the alpha channel with another? For example, if I had the RGB and alpha as separate PNG files (24 and 8 bit, respectively), I would…
EllipticalInitial
  • 1,800
2
votes
1 answer

Alpha plugin in GStreamer not working

I'm trying to compose two videos, and I'm using the alpha plug-in to make the white color transparent. To test the alpha plug-in I'm creating the pipeline with gst-launch. The first test I done was: gst-launch videotestsrc pattern=smpte75 ! alpha…
Miguel Escriva
  • 21
1
2 3