How to use the Composition Overlay Tool
- Open an image. Click Open an image, drop a file on it or paste one. A photo, a scan of a painting, a thumbnail sketch or a screenshot of a work in progress all work, and the file never leaves your device. The sunset coast is a sample to experiment with.
- Pick overlays. Click the chips to switch on Rule of thirds, Phi grid, Golden spiral, Golden triangles, Dynamic symmetry, Diagonal method, Center cross or a Custom grid with your own columns and rows. Several can be on at once, each in its own color.
- Turn the spiral and triangles. Rotate (key O) and Mirror (key M) step through all eight orientations of the spiral. Tick Exact golden rectangle to see the true curve instead of one stretched to your frame.
- Test a crop. Choose a ratio under Test a crop, drag the frame or use the arrow keys, and tighten it with Crop zoom. The overlays are always drawn for the cropped frame, and the line under the image shows its exact pixel size and ratio.
- Style and export. Choose Per overlay colors or One color, set width and opacity, and keep the dark halo for light images. Download PNG saves the cropped image with the lines; Overlay only PNG and Overlay SVG save just the lines on a transparent background at the same size.
What these guides measure, and what they can’t
Composition guides are not rules a good picture must obey. They are ways of asking where the eye lands and whether the main shapes relate to the edges of the frame. Every one of them divides the rectangle by a different logic, so a focal point can sit “on” one guide and miss another by a wide margin.
The rule of thirds splits each side at 33.3% and 66.7%. The phi grid splits at 38.2% and 61.8%, the golden section, so its intersections sit closer to the center. The difference is 4.9% of the width, about 290 pixels on a 6000-pixel photo, which is visible but small; if a subject lands between the two, both guides agree it is off center in a pleasing way.
The golden spiral comes from cutting a square off a golden rectangle again and again. Its eye, where the curve converges, sits 27.6% in from two edges, farther out than either the thirds or the phi intersections. In a true golden rectangle that eye coincides exactly with the point where the golden triangles meet, at 72.4% along the diagonal.
Dynamic symmetry, set out by Jay Hambidge in his 1920 book Dynamic Symmetry: The Greek Vase, works from the rectangle’s own diagonals. A reciprocal is a line from a corner that meets a diagonal at a right angle; where it reaches the far side it marks a smaller rectangle with the same shape as the whole. The diagonal method looks at the four 45° lines from the corners instead, on the observation that details often fall along them.
How the geometry shifts with the frame
Thirds and phi lines stay at the same percentages in every frame. The diagonal-based guides move with the frame’s shape, and this tool computes them for the actual proportions, never a template. Positions below are measured along the long side of a landscape frame:
| Frame | Reciprocal lines | 45° lines reach the long edge at | Golden-triangle intersections | Golden spiral fit |
|---|---|---|---|---|
| 1:1 square | same as the diagonals | the corners | 50% (center) | squeezed 38.2% |
| 5:4 (8 × 10 in) | 36% and 64% | 80% | 61.0% | squeezed 22.7% |
| 4:3 | 43.8% and 56.3% | 75% | 64.0% | squeezed 17.6% |
| 1.414 (A4, A3) | both at 50% | 70.7% | 66.7% | squeezed 12.6% |
| 3:2 (35 mm) | 44.4% and 55.6% | 66.7% | 69.2% | squeezed 7.3% |
| 1.618 golden | 38.2% and 61.8% | 61.8% | 72.4% | exact |
| 16:9 | 31.6% and 68.4% | 56.3% | 76.0% | stretched 9.9% |
A few things fall out of the arithmetic. In an A-series sheet the two reciprocals meet at the center line: half of a 1.414 rectangle is another 1.414 rectangle, the same property that lets A4 fold into two A5 sheets. In a 3:2 frame the 45° lines reach the edge exactly on the thirds lines, so the diagonal method and the rule of thirds agree there. In a golden rectangle the reciprocals land on the phi grid, and every guide based on φ lines up.
The spiral column explains the Exact golden rectangle option. A golden spiral only fits a 1.618 frame, so most software stretches it to whatever frame you have, which warps the curve. On a square it is squeezed by over a third. The tool says how much distortion your frame introduces and can draw the true spiral, centered, instead.
Tips from practice
Try several guides, and be suspicious of a perfect fit. With eight overlays and eight spiral orientations, almost any image will line up with something. A guide is useful when it shows you a problem, such as a horizon cutting the frame in half or a focal point jammed against the edge, rather than when it confirms a choice after the fact.
Look for the picture inside the picture. Crops change the geometry as much as the content. A 4:5 crop of a 3:2 landscape moves the reciprocals, the triangle intersections and the spiral’s eye, and often finds a stronger composition hiding in the original.
Put the overlay on its own layer. Overlay only PNG has the exact pixel size of the frame, so in Procreate, Photoshop or Krita you can import it as a layer, lower its opacity, and toggle it while you paint instead of exporting screenshots back and forth.
Plan in thumbnails, check in overlays. Draw small value thumbnails first, then photograph the best one and test it here. Moving a shape on a 3-inch thumbnail is free. The Notan & Value Study Tool helps check that the light and dark pattern supports the same focal point the geometry does.