Layer masks
How to Use a Layer Mask in Photasium
A corner you want gone for a post, a table around a product, or a name in a screenshot can be hidden while the pixels stay in the layer. In Photasium that happens in the tab: the file never goes to a server.
Hiding pixels on the layer
A layer mask sits beside the raster and decides what shows. A light colour on the mask shows the layer, and a dark colour hides it. Opacity below 100 shows it only part of the way. The pixels stay on the layer, so a later stroke can paint them back.
Eraser removes pixels from the raster. Remove background can build a mask around a subject and leave you painting the edge. Add layer mask starts with the whole layer visible, or with only a selection visible if one is active, and you paint the rest.
A corner the story does not need
A story often has a lamp, a passer-by, or a bright window that pulls the eye. Paint that area with a dark colour on the mask and leave the person. If the frame changes, a light colour paints the window back.
Duplicate the raster first if you want an unmasked copy still in the stack. Layers keeps that copy.
A listing can keep the product and hide the table. A low hardness feathers the edge where the product meets the cloth. Remove background finds the subject when the edge is simple. Paint the mask when hair, glass, or a thin handle needs a stroke at a time.
A screenshot can include a name, an email, or a number you do not want to share. Paint that corner on the mask so the rest of the window stays readable. Turn mask off if you need the original words again, and the hide comes back when you turn the mask on.
A scan with a shadow along one edge can hide that band with a large, soft stroke, so the page keeps its tone. The shadow pixels stay in the layer. Turn mask off if the band should come back for a different crop.
Masking a layer in Photasium
Open a photo
Open the editor, then File → Open, or drop an image on the canvas. Select a raster layer in the Layers panel.
Add a layer mask
Click Add layer mask in the Layers footer, or right-click the row and choose Add layer mask. The same command is on the button at the end of the row. With no selection, the mask is white and the whole layer stays visible. With a selection, the mask shows those pixels and hides the rest. The mask thumbnail is selected, so the next stroke paints the mask. The footer button is disabled once a mask is there, because a layer holds one mask.
Paint the mask
Click Brush, or press B. Size runs from 1 to 500 and starts at 24. Hardness runs from 0 to 100 and starts at 80. Opacity runs from 1 to 100 and starts at 100. Press [ or ] to change size while you work. The foreground colour starts black, so a stroke in that colour hides. A light colour, including white, shows the layer again. Eraser (E) hides. The options bar says you are painting on the layer mask, where dark colours hide the layer and light colours show it. Click the layer thumbnail when you want Brush back on the photo. Picker (I) samples a colour from the photo into the foreground well.
Show, apply, or delete
Right-click the row. Turn mask off shows the whole layer and keeps the mask. A stroke on the mask thumbnail still changes it. Turn mask on brings the hide back. Apply mask writes the hide into the pixels and removes the mask. Delete mask asks you to confirm, then the hidden pixels show again. Undo after any of these brings the previous mask back.
Add layer mask needs an unlocked raster layer. On a text layer or a group the footer button stays disabled: rasterize type from the layer menu, or open a raster inside the group. On a locked raster the button reports that the layer is locked. Apply mask and Delete mask stay disabled until you unlock the layer. Turn mask off still works on a locked layer. If a selection is active while you paint, the stroke stays inside it.
Brush, Eraser, Blur, and Smudge follow the mask thumbnail. Blur softens the edge of the hide. Smudge drags the mask along the stroke. Dodge, Burn, Sponge, Heal, Fill, and Gradient keep painting the photo, even while the mask thumbnail is selected. Remove background can also leave you on a mask: choose Hide the background with a layer mask, and the mask thumbnail starts selected.
Where the mask hides the layer, whatever is behind it shows through: another layer, or the document background. A photo you open uses a transparent background, so the editor draws a checkerboard there. PNG and WebP keep those pixels clear. JPEG fills them with white.
The pixels stay in the layer
The mask sits beside the raster you painted, nothing was uploaded, and undo brings the previous mask back. If the hide is too wide, paint with a light colour, or undo and use a smaller brush.
Download PNG, JPEG, or WebP if you need a file to send. Come back later and the document is still listed under the editor, until this browser’s storage is cleared. A layer mask sits with the other photo editing tools: paint or erase, keep a stroke inside a selection, and export a listing.