Make background transparent

[jgt1942]

I cannot find the how-to for making the background transparent and saving it so I can use it in other applications. I have a few B&W images, e.g. the black image is on a white background. I want the white to be transparent.

[jgt1942]

I just found tanel_pluginpack_20120305.zip and installed it. 

• I opened my image and selected it
• I then clicked Effects > Color > Color to Alpha
• The "Color to Alpha" window opens, now I can see my image and the white background is now transparent
• I saved the image as a PNG file
• I then attempted to use the image by inserting it in a PDF file but the entire image that is inserted is black. What the heck did I do wrong?

 

[BoltBait]

When saving as PNG, make sure to choose "auto" or "32-bit" to preserve transparency.

[jgt1942]

OK where do I choose "auto" or "32-bit"?

When I saved I clicked File > Save As > used the same folder as the original but changed the name so I could keep the original file.

Sorry to be so dense.

[BoltBait]

15 minutes ago, jgt1942 said:

OK where do I choose "auto" or "32-bit"?

 

After you choose the filename, click OK and you'll get the "Save Configuration" screen. This asks the bit depth.

[jgt1942]

AH yes I did see that window. Originally I had selected "Auto-detect", I now selected 32-bit but still, I get a black image when I use it or view it with IfranView. In the "Save Configuration" window where I can select the "Bit Depth" the background in the preview looks like it is transparent (it looks like a checkerboard). I've got to run and will not be available for several hours. Much thanks for the feedback.

[BoltBait]

If you want, you can post one of your transparent images here and someone will be glad to check to see if it is indeed saving in the proper format.

 

Other than that, I'm guessing that the issue is with the other software and not Paint.NET itself.

[jgt1942]

Great suggestion.  I've uploaded two files

test01.png (the first file below) is the original file

test01-trans.png is the file I've modified and should have a transparent BG. I'm surprised that it displays in the webpage. When I attempt to insert it in another file (PDF for example) or open it with IframView all I see is a black square.

Edited May 30, 2018 by jgt1942
identify which image is the original (source) file

[jgt1942]

OK I think I was doing something stupid but I'm not sure what I did. I've managed to make the background transparent just by repeating what I think I've been doing all along. Here is the latest file and it has the transparent BG.

[NinthDesertDude]

You can convert black-and-white photos to have transparent backgrounds with 100% accuracy using the Switch Gray to Alpha plugin.

[windydick]

Hi, I'm a newbie finding my way round, graduating from W10 Paint with some difficulty.  Alphas and plug-ins are way above my pay-grade at mo.  What you could try is magic wand a white portion, either contiguous or global as appropriate.  Then simply delete the magic wand selection, which then becomes transparent.  Also try try tinkering with tolerance for the magic wand selection as there's no gradient between solid off-white and transparent no pixel.

My problem why I'm here is dear old Paint's transparent/opaque toggle, which I can't find here.  Even copy/paste or move a selection on a transparent background obliterates everything in the selection area.  You paste transparency, not nothing, if you see what I mean.  Paste in new layer works a bit clunky, but even more fiddly to "toggle" back to opaque.

[toe_head2001]

3 minutes ago, windydick said:

... You paste transparency, not nothing ...

 

When you paste, you're overriding the RGBA values, rather than compositing them.

The RGBA values are composited when using layers, and that's why pasting into a new layer works the way you expect.

[windydick]

 This is .png of magic wand>delete on your first sample image.  I think it's a lot better than your second image if you look at the tongue zig-zag, etc.  Confusingly it displays with a PDN chequer background in Honeyview, but not in Windows Photo.

I've just made a .pdn with a white background layer, but I find that .pdn is not an allowed file, which I find really, really, really strange!!!  I've a lot to learn!

If you're interested, here's a link to the .pdn file on my Google Drive;

https://drive.google.com/open?id=1gNOqll5_ON2q0FQRn4gu33ZTMkGpAxgu

 

[MJW]

The Magic Wand approach is a bad way  to make the background transparent for a black-on-white image like the snail drawing. Do as @Joshua Lamusga suggests: use a plugin that converts white to transparent, such as Switch Gray to Alpha  or Color Clearer. There are a number of others that will also work, such as the Grim Color Reaper.

 

The problem with using the Magic Wand is that most black-on-white images contain gray pixels on the edges of the black areas, to make the edges look smooth, not jagged. If the tolerance of the Magic Wand is set high when selecting the background, so that all non-black pixels are selected, these pixels will be deleted, distorting the image and leaving a jaggy edge. If the tolerance is set low, so that only the truly white pixels are selected, the gray pixels will remain, and if the edited image is placed over a colored background,  will be clearly visible as a jagged gray halo. Using one of the white-to-transparent plugins will convert the gray pixels to partially-transparent black pixels.

[windydick]

Hi, yes, MJW - I guessed and accept the deficiencies you describe.  However, the result on my attempt is clearly considerably better than jgt1942's second sample above - compare almost anywhere on the image, which shows the faults you describe.  OK, on a solid white background.  Horses for courses, I suppose; probably much worse results with grey-scale photos, and coloured background.  wd

[MJW]

@windydick I suggest you just bite the bullet and install a plugin. It's not that hard to do, and once you have the plugin, eliminating the white background will be easier, and much better, than using the Magic Wand.

 

You can install BoltBait's plugin pack, which includes Switch Gray to Alpha, among many other useful plugins. The plugin pack has an installer, which will do most of the work for you. Installing the plugins should be as easy as, or easier than, installing Paint.NET. Running the plugin is as easy as running a built-in effect. You won't even know the difference.