Image Mask
A grayscale (or alpha) channel that defines which parts of an image are visible, semi-transparent, or hidden.
An image mask is a separate channel — usually stored as the alpha channel of a PNG or as a dedicated layer in PSD — that determines the opacity of each pixel in the final image. A pixel with a mask value of 0 is fully transparent, 255 is fully opaque, and anything in between is partially see-through.
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An image mask is a separate channel — usually stored as the alpha channel of a PNG or as a dedicated layer in PSD — that determines the opacity of each pixel in the final image. A pixel with a mask value of 0 is fully transparent, 255 is fully opaque, and anything in between is partially see-through. The mask is what makes a flyaway hair edge look natural, what makes a glass effect look like glass, and what makes a logo composite onto any background.
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Most commonly as the alpha channel of a 32-bit PNG. Also as a dedicated layer in PSD files, as a separate file (mask.png) alongside the main image, or as a CSS mask-image in web design.
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A binary mask is either 0 or 255 — fully transparent or fully opaque, with a hard edge. A soft mask uses intermediate values (50, 128, 200) to create a gradient of transparency, which is what makes a flyaway hair edge look natural.
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Modern AI background removers output a per-pixel mask, then convert it to the alpha channel of a 32-bit PNG. The mask can be edited in Photoshop (or any image editor that supports alpha) to refine specific regions.
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Cut out the subject, save the transparent PNG, drop it onto any background. To refine a rough edge, paint the alpha channel with a soft brush in Photoshop. To composite multiple subjects, layer the transparent PNGs and adjust the alpha of each layer.
A binary mask is either 0 or 255 — hard edge, no in-between. A soft mask uses intermediate values (50, 128, 200) to create a gradient of transparency, which is what makes a flyaway hair edge look natural. Most modern AI tools output soft masks by default.
Continue learning
What is an Alpha Channel?
The technical deep-dive on the alpha channel.
What is RGBA?
The four-channel colour model that includes the alpha channel.
How AI Background Removers Actually Work
A non-technical explanation of the segmentation models behind the tool.
Apply this to your workflow
BGRemover turns the technical parts of background removal into a single click. Open the workspace and see the difference.