Black/White JPG Logo to Transparent PNG - Bitmap Mask ?

[Carlos]

I have a black logo on a white backbround as a JPG image.

I would like to make all the White transparent (alpha channel), so that I can save it as a Black Logo on a Transparent background PNG.

 

What is the cleanest/ most accurate way to do this, please?

Using a bitmap image as a mask is ideally what I need (copy the inverted greyscale image into the alpha channel to get the transparency)

 

any help is really appreciated.

 

I have Affinity Designer & Photo beta.

[Leigh]

Depending on how complex the logo is, I would use the Flood Eraser Tool in Affinity Photo. You can use the Tolerance slider from the context toolbar to adjust the range of pixels affected when using this tool. Once you've removed the white background you can go to File > Export... > PNG and select Selection without background from the Export drop down.

[Carlos]

@Leigh - thanks for your reply, the Logo is quite complex, so I wanted to avoid using "Tolerance' based tools.

As an example in Photoshop, I would add an Alpha Channel to the RGB image, and simply paste the black/white image into the Alpha Channel.

 

There is a thread that says that bitmap images can be used as masks (I just don't know how to)

https://forum.affinity.serif.com/index.php?/topic/1450-mask-questionhelp/

[My Strawberry Monkey]

Have you tried FILTERS > COLOURS > ERASE WHITE PAPER Or SELECT > SELECT SAMPLED COLOUR  in Photo?

 

Again it will depend on the image and how complex it is and if the BG is pure white, I have tried both of these options on various logos and have achieved the desired effect for me.

[Carlos]

@mystrawberrymonkey

thanks for your Affinity Photo suggestion.

It isn't the cleanest/best solution, but the result is OK and more than useable until the bitmap image mask method is explained.

 

The BG is pure white, the FG is black, it is just the edges (greyscale antialiased edges) that could be better, which is why I prefer to copy the BW image straight into the Alpha channel.

For the moment though it will be fine for a test version.

:)

[My Strawberry Monkey]

Hi Carlos,

 

Glad you found it useful. There is another thread https://forum.affinity.serif.com/index.php?/topic/8293-affinity-photo-how-to-elegantly-erase-unwanted-colors/

where MEB about 4 posts down suggests another method.

 

Copying the image into the alpha channel is not something that i'm aware of, but if there is a way i'm sure it would be useful to know.

 

Allan

[ronniemcbride]

Hey Carlos! do you mind sharing/showing the log design with us? 

 

How about a more no destructive method like select > select color range and then click the black part the refine button and use the refine tool. part of this technique was used in my video for creating custom brushes.

 

[MEB]

Hi Carlos,

Select your image (jpg), go to menu Layer ▹ Rasterize to Mask. You can then attach the mask to whatever object you want.

[Carlos]

Hi Carlos,

Select your image (jpg), go to menu Layer ▹ Rasterize to Mask. You can then attach the mask to whatever object you want.

Hello MEB, That works great, it does the job & is easy to use. :) Thank You

 

(Thanks also to Leigh, mystrawberrymonkey, & ronniemcbride for your suggestions & time ;))

Chroma/Luma keying techniques is what I wanted to avoid, straight forward Channel chopping was all I was after, for the cleanest/accurate result; i'm from a vfx background (Shake/Nuke compositing) so basic image operations was all i needed.

 

If anyone is interested in the original method i wanted to use > My original image was RGB, lets say 24bit, I wanted to bump it up to 32bit image RGBA and use the last 8bits for transparency, the Alpha channel is just a black/white grayscale image, so you can just paste/draw in any values between black & white (including various shades of 'grey'). So the original B/W image was perfect to use as the Alpha channel (for transparency).