Contact Shadow

Contact Shadow puts a soft shadow under a transparent cutout so it stops looking like it is floating. It runs on your device, needs no model download, and changes nothing about the subject itself.

Why a clean cutout still looks wrong

An object sitting on a surface blocks some of the light that would otherwise reach the surface immediately around it. That darkening is not decoration, it is most of the evidence your eye uses to decide the object is resting on something rather than hovering over it.

Removing a background removes that evidence along with everything else, because the shadow was part of the background. So a cutout can have a perfect edge and still read as a sticker, and the fix is not a better edge.

What this tool actually does

Four operations, in order, all of them on the alpha channel your cutout already carries.

1. Find the contact line. The lowest row of the image that is at least half subject. Not the lowest row with any transparency at all: a cutout fades to nothing over a few pixels at its boundary, and grounding on the faintest of those floats the shadow by exactly the width of that fade.
2. Squash the outline toward that line. The silhouette is compressed vertically so it occupies a fraction of the height the subject occupied. That is what turns a shape into a footprint.
3. Offset and blur it. A small move down, then three passes of a box blur, which is the standard cheap approximation of a Gaussian.
4. Composite your pixels back on top. The shadow goes underneath; your subject is untouched.

Nothing was trained, nothing is fetched, and the same file with the same settings always produces the same bytes. This is not generation and the tool never describes it as such.

The three presets

Every distance is a fraction of your subject own bounding box rather than of the image, which is why one preset looks right on a 400 pixel thumbnail and on a 4000 pixel product shot, and on a tall bottle and a wide box alike.

• Contact keeps the shadow tight and relatively dark under the object. This is what something resting directly on a surface casts, and it is the right default for a product on a white listing page.
• Soft spreads it wider and fades it, as though the light source were a window rather than a lamp. It suits rounded and organic shapes.
• Drop does not compress the silhouette at all. It offsets it down and to the right so the shape reads as itself. That is a graphic effect rather than a physical one, and the tool says so where it is offered: no object sitting on a surface casts an uncompressed copy of its own outline.

Choosing a preset resets the strength slider to that preset own default, because the strength is part of what makes each one look like what it is called. A contact shadow as faint as a soft one is simply a soft one.

Why your image sometimes comes back larger

The shadow is offset below the subject and blurred outward. If the subject already touches the bottom of the frame, there is nowhere for it to go and it would be clipped.

So this page adds as much canvas as the offset and the blur need, on every side, and tells you how much it added. The added area is fully transparent, so it costs nothing visually and you can crop it away.

The growth stops at 512 pixels a side. That is enough for every ordinary case, and on a very large image at the Soft setting the blur alone can reach further, because the blur is measured as a fraction of your subject height. When that happens the result says the shadow is clipped instead of claiming it is not, and the fix is a tighter style rather than a lower strength.

There is no version of this in the image editor

That is a limitation worth explaining rather than a gap somebody forgot to fill.

The image editor does not hold a cutout. It holds your original photograph and, separately, the selection that says which pixels are the subject, and it combines the two only at the moment it draws to the screen. A contact shadow goes underneath a cutout. Underneath an opaque photograph there is nothing to show through, so the run would complete, report success, and change nothing at all. Even if the shadow were painted onto the photograph instead, it would land outside your selection and the editor would hide it again on the next redraw.

Both of those are properties of the editor rather than of this tool, and both would have to change first. Use the editor to get the cutout right, then bring the transparent PNG here.

What it cannot do

A matte tells the tool the silhouette and nothing about the shape. It cannot know which parts of an object are nearest the surface, so the shadow is a footprint of the outline rather than a traced projection of a solid.

For a bottle, a box or a shoe photographed from roughly eye level, that is close enough to convince, because the silhouette and the footprint very nearly agree. For something photographed from above, or something with a large overhang, they do not agree at all, and no setting on this page will make them.

Two more limits worth stating plainly:

• It assumes one light. Two lights cast two shadows, and there is nothing in a cutout that could tell the tool how many there were.
• It does not shade the object itself. A real object sitting on a bright surface catches bounced light along its base. Adding that would mean changing your pixels rather than adding underneath them, and this tool does not change your pixels.

If it looks wrong

• The shadow seems detached from the object. The cutout has a soft fringe along its bottom edge, so the contact line is being found below where the object really ends. That is worth fixing in the cutout rather than here.
• It looks heavy. Bring the strength down before reaching for a different preset. Real contact shadows are darker than people expect directly under the object and fade quickly, which is why a low-strength Contact usually beats a high-strength Soft.
• The tool refuses your file. It needs transparency, and an ordinary photograph has none: every pixel is opaque, so there is no outline. Run it through the background remover first. The tool refuses rather than handing back an unchanged file and reporting success.

What to do next

If the composite still looks wrong once the shadow is there, the remaining cause is usually colour rather than grounding. Cutout Match measures the colour temperature, contrast and light direction of the background you are placing the subject on and moves the subject toward them, also with no download.