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Chapter 17 · The filter catalogue
The Filter menu is the longest menu in Photopea and the one most often described in vague terms. "It has the usual filters" is not useful if you are trying to decide whether a specific effect exists, and it is exactly the kind of thin claim that makes a reference page worthless. So this chapter lists the filters by group, alphabetically within each group, with the parameters each one exposes. If a filter is not in this list, it is not in the application.
One structural note before the catalogue. Photopea applies filters to the active layer, or to the selection if one exists, and it applies them destructively unless you convert the layer to a smart object first. A smart object turns every filter into a live, re-editable effect with its own mask, which is why the smart-object workflow described in chapter 03 matters so much for filter work. Filters also respect the document's bit depth: a handful of them behave differently or are unavailable at 32-bit, and the difference is noted where it is relevant.
Blur
The Blur group contains nine filters, and the distinction between them is not cosmetic — each uses a different kernel and produces a visibly different result on the same image.
| Filter | Parameters | Character |
|---|---|---|
| Average | None | Fills the selection with its single average colour |
| Blur | None | A fixed, very small radius; useful for softening a hard edge by one pixel |
| Blur More | None | Roughly three times Blur; still fixed |
| Box Blur | Radius | A square kernel; fast and mechanical, with visible boxiness at large radii |
| Gaussian Blur | Radius | The default choice; smooth, isotropic and the basis of most soft-focus work |
| Lens Blur | Radius, blade curvature, rotation, brightness, threshold, noise, distribution | Simulates a physical aperture; produces polygonal bokeh highlights |
| Motion Blur | Angle, distance | A straight directional smear; the classic speed effect |
| Radial Blur | Amount, method (Spin or Zoom), quality, centre | Rotational or zoom smear around a movable centre point |
| Surface Blur | Radius, threshold | Edge-preserving; smooths flat areas while keeping boundaries, which makes it a skin-smoothing tool |
The pairing worth remembering is Gaussian for general softening and Surface for retouching. Gaussian blurs everything equally, including the edges you wanted to keep; Surface Blur's threshold parameter tells it how different a neighbouring pixel must be before it is treated as an edge and preserved. Set the radius high and the threshold low and you get a plastic look; set the radius moderate and the threshold around 15 to 20 and you get skin that reads as smooth without losing pore structure entirely.
Blur Gallery
Blur Gallery is a separate submenu because its five filters share an on-canvas interface rather than a slider dialog. Field Blur places multiple pins with individual blur amounts and interpolates between them. Iris Blur uses an elliptical focus region with handles for the ellipse, feather and falloff. Tilt-Shift uses two parallel lines to define a sharp band. Path Blur blurs along a drawn path, producing curved motion blur. Spin Blur blurs rotationally around a circular widget. All five are covered in more detail in chapter 16 alongside their shared Blur Effects and Noise panels.
Sharpen
Five sharpen filters, and the difference between them is the difference between unusable and professional.
| Filter | Parameters | Notes |
|---|---|---|
| Sharpen | None | A fixed small unsharp mask; almost always too crude |
| Sharpen Edges | None | Applies the same fixed amount only where contrast is detected |
| Sharpen More | None | A stronger fixed amount |
| Unsharp Mask | Amount, radius, threshold | The only one with real control; amount sets strength, radius sets the edge width sampled, threshold suppresses sharpening in flat areas |
| Smart Sharpen | Amount, radius, reduce noise, remove (Gaussian / Lens / Motion), angle, tonal width, fade | Sharpens with a noise-reduction stage and per-tone control |
Unsharp Mask is the filter to use. The parameters interact in a way that is worth internalising: a radius around 1.0 pixel sharpens fine detail, a radius around 2.0 to 3.0 sharpens structure, and a threshold around 3 to 5 prevents noise from being amplified. Over-sharpening is visible as a bright halo along high-contrast edges, and the cure is a smaller radius rather than a smaller amount — halos are a radius artefact, not a strength artefact.
Noise
| Filter | Parameters | Use |
|---|---|---|
| Add Noise | Amount, distribution (Uniform / Gaussian), monochromatic | Adds grain; monochromatic keeps it luminance-only, which reads as film rather than as colour speckle |
| Despeckle | None | A single-pass median; removes isolated speckles without a dialog |
| Dust & Scratches | Radius, threshold | Targets small isolated defects; the threshold protects real detail |
| Median | Radius | A median filter; excellent for salt-and-pepper noise and for a painterly base |
| Reduce Noise | Strength, preserve details, reduce colour noise, sharpen details, per-channel | The full noise-reduction dialog; the colour-noise slider is the one that fixes high-ISO chroma blotches |
The distinction that matters here is luminance noise versus colour noise. Luminance noise looks like grain and is often acceptable or even desirable; colour noise looks like coloured blotches and almost never is. Reduce Noise lets you attack them separately, and the correct default is to push the colour-noise slider hard and the strength slider gently.
Distort
Nine distort filters, all of which remap pixel positions rather than pixel values. Because they move pixels, they always soften the result slightly and they always resample, so applying a distort filter twice is never the same as applying a stronger version once.
| Filter | Parameters | Effect |
|---|---|---|
| Displace | Horizontal and vertical scale, displacement map, stretch/ tile, undefined areas | Warps using a second image as a height map; the most powerful and least used distort filter |
| Pinch | Amount | Pulls pixels toward the centre of the selection |
| Polar Coordinates | Rectangular to Polar, Polar to Rectangular | Converts between linear and radial layouts; the basis of the classic "little planet" effect |
| Ripple | Amount, size (Small / Medium / Large) | Concentric waves; good for water and for flag-like distortion |
| Shear | Curve, wrap or repeat edges | Bends the image along a vertical curve |
| Spherize | Amount, mode (Normal / Horizontal / Vertical) | Bulges or pinches toward a sphere |
| Twirl | Angle | Rotates pixels around the centre with a falloff; the swirl effect |
| Wave | Generators, wavelength, amplitude, scale, type, randomise | A configurable wave; far more controllable than Ripple |
| ZigZag | Amount, ridges, style (Around Centre / Out From Centre / Pond Ripples) | Concentric zigzag ripples |
Displace deserves a specific mention because it is the filter that produces convincing texture mapping without a 3D engine. You supply a greyscale image as the displacement map, set the horizontal and vertical scale, and every pixel of the target shifts according to the brightness of the corresponding pixel in the map. A soft cloud map produces an organic warp; a hard-edged map produces a mechanical one. It is the closest thing in the application to a procedural distortion system.
Pixelate
| Filter | Parameters | Effect |
|---|---|---|
| Color Halftone | Max radius, screen angles per channel | Simulates a printed halftone screen with per-channel dot angles |
| Crystallize | Cell size | Clusters pixels into flat polygonal cells |
| Facet | None | Groups similar-coloured pixels into flat facets |
| Fragment | None | Creates four offset copies averaged together; a soft, blurry displacement |
| Mezzotint | Type (dots, lines, strokes, grain) | Converts to a stochastic pattern; useful as a mask generator |
| Mosaic | Cell size | The classic pixelation; each cell becomes one colour |
| Pointillize | Cell size | Scatters coloured dots on a background; a painterly pixelate |
Render
| Filter | Parameters | Effect |
|---|---|---|
| Clouds | None (uses foreground and background colours) | Fractal noise between the two colours; the standard texture base |
| Difference Clouds | None | As Clouds, but blended with the existing layer using Difference; repeatable for vein-like patterns |
| Fibers | Variance, strength, seed | Vertical fibre texture; the basis of hair, wood and brushed-metal looks |
| Lens Flare | Brightness, flare centre, lens type (50-105mm, 35mm, 105mm) | A simulated optical flare with three lens profiles |
| Lighting Effects | Style presets, light type (Point / Directional / Spot / Omni), intensity, focus, gloss, material, exposure, ambience, texture channel, height | A full lighting model with a movable light widget on the canvas |
Lighting Effects is the outlier in this group and one of the most capable filters in the application. It treats the layer's luminance or a chosen alpha channel as a height map and lights it as a surface, which means a flat texture can be given real relief. The texture-channel dropdown is what makes it useful beyond the presets: point it at a channel that holds a bump map and the filter produces embossed shading that follows the map rather than the colour.
Stylize
| Filter | Parameters | Effect |
|---|---|---|
| Diffuse | Mode (Normal / Darken Only / Lighten Only), amount | Scatters pixels randomly; a rough, hand-drawn edge |
| Emboss | Angle, height, amount | Greyscale relief; the classic 1990s emboss |
| Extrude | Type (Blocks / Pyramids), size, depth, solid front faces, mask incomplete blocks | Explodes the image into 3D-looking blocks or pyramids |
| Find Edges | None | Traces edges as dark lines on white; the fastest edge extractor |
| Glowing Edges | Edge width, brightness, smoothness | As Find Edges but inverted and coloured, producing neon outlines |
| Oil Paint | Stylisation, cleanliness, scale, bristle detail, lighting, angle, shine | A full painterly renderer with brush-scale and lighting controls |
| Solarize | None | Inverts everything above the midpoint; a partial negative |
| Tiles | Number of tiles, maximum offset, fill (background / foreground / inverse / unaltered) | Splits the image into offset tiles |
| Trace Contour | Level, edge (lower / upper) | Draws a single contour line at a chosen luminance |
| Wind | Method (Wind / Blast / Stagger), direction (from right / from left) | Horizontal streaks; the classic wind effect |
Oil Paint is worth flagging because it is a modern, parameter-rich renderer rather than a legacy effect. Stylisation controls how far the brush strokes deviate from the source, cleanliness controls how much of the original colour survives, and scale controls stroke size. At low stylisation and small scale it produces a subtle painterly softening that is genuinely useful on portraits; at high settings it produces something closer to an illustration.
Other
| Filter | Parameters | Effect |
|---|---|---|
| Custom | A 5×5 kernel matrix, scale, offset | Convolution by hand; the filter that can reproduce almost any other linear filter |
| High Pass | Radius | Removes low frequencies and leaves a grey image with edges; the basis of the high-pass sharpening technique |
| Maximum | Radius, preserve (squareness / roundness) | Expands light areas; a dilate operation |
| Minimum | Radius, preserve (squareness / roundness) | Expands dark areas; an erode operation |
| Offset | Horizontal and vertical shift, undefined area handling | Shifts the image by a pixel amount; essential for making seamless tiles |
High Pass and Offset are the two "other" filters that earn their place in a regular workflow. High Pass used with a Overlay or Soft Light blend mode is a sharpening method that avoids the halos of Unsharp Mask, because it isolates edge frequencies rather than amplifying contrast around edges. Offset used with the wrap option and then healed is the standard technique for turning a texture into a seamless tile, and it is the reason the filter exists at all.
What the filter menu reveals
Counting the catalogue produces a number worth stating plainly: Photopea ships roughly sixty individual filters across eight groups, and the coverage is close to complete for two-dimensional raster work. The groups that a desktop editor would add and Photopea does not have are the ones tied to other media — there is no 3D group, no Video group, no Vanishing Point as a filter (it is a separate workspace, covered in chapter 16), and no full Camera Raw Filter entry because Camera Raw is a layer-level workspace rather than a menu filter. There is also no Filter Gallery in the desktop sense of a single dialog hosting dozens of artistic effects; the artistic effects are individual menu items instead.
The practical reading is that the filter menu is not a weak point. Where Photopea is thin is not filters but print and motion, and the filter catalogue is one of the places where the application is strongest. Chapter 18 completes the inventory with the twenty-seven blend modes that determine how all of these filtered layers combine.