Photographing another screen

When the puzzle is on one device and the solver on another, you can photograph the screen. A photo imports well when the grid lines stay straight and every dot keeps its own color. The solver doesn't remove glare or stripes. It straightens the board from four corners and reads the color in the middle of each cell, so a reflection or color shift goes straight into the board.

A screenshot taken on the other device and sent across is always cleaner (see Taking a screenshot that imports cleanly).

Prepare the screen you're photographing

Open the level fresh. Drawn paths read as extra dots, just as in a screenshot.
Turn the brightness up to medium-high. At low brightness many phone screens flicker, and the flicker shows up in photos as dark horizontal bands.
Turn off color filters such as Night Shift, a blue-light filter or an "eye comfort" mode. They tint the screen warm, which shifts blues toward purple and whites toward yellow.
Lay the device flat or prop it where no lamp, window or ceiling light reflects in the glass.

Glare

Glare is the most common reason a photographed board comes back wrong. Over an empty cell, a strong reflection can be read as an extra pale dot. Over a dot, it pushes the color toward white, so the dot may join the wrong color or get a color of its own.

Before you shoot, look at the screen from where the camera will be. If you see a light in the glass, tilt the device, switch the light off, or move. A dark screen also reflects you, so shoot slightly from the side if your silhouette lands on the board. Screen protectors and cracked glass add haze and reflections of their own.

Moiré and stripes

Photos of screens often show rainbow ripples called moiré. They appear when the camera's sensor grid and the screen's tiny red, green and blue elements interfere. Strong moiré can give an empty cell enough color to look like a dot, or shift the hue of a real one.

Moiré changes quickly with distance and angle. If you see it on your camera screen, move a little closer or farther, rotate the camera a few degrees, or switch to the 2× lens. Bands that move between shots are flicker, and raising the source brightness usually removes them.

Angle and distance

Hold the camera parallel to the screen, centered over the board. The solver corrects tilt when it straightens the board, but the far side of a tilted board gets fewer pixels and is often out of focus.

Fill most of the frame with the board. The solver scales every image to 1,600 pixels on its long side before reading it. A board that spans a third of a portrait photo's width ends up about 400 pixels across, under 30 pixels per cell on a 15 × 15 board. That leaves little room for blur or glare.

Don't go too close either. The wide main lens bends straight lines near the edges of the frame, and the straightening assumes straight edges, so a bent edge shifts the middle rows. The 2× lens from 20 to 30 cm away keeps edges straight and the board large. Tap the board on your camera screen to focus there, and hold still, because a blurred dot can spread into the next cell.

Cropping before you import

Cropping the photo in your gallery app first is worthwhile. With less of the room in the picture, the board keeps more detail after scaling. Keep the whole board and a small margin. The corner handles can't leave the image, so a grid corner cut off by the crop can't be placed.

Moving the four corners

The automatic outline is meant for screenshots with perfectly even grid spacing. Perspective makes the spacing uneven, so photos usually stop at Line up the board for you to place the corners.

Drag each yellow handle onto an outer corner of the playing grid, where the outermost grid lines meet. Ignore the screen's edge and any frame drawn around the board. While you drag, a magnifier near the top of the image, on the side away from your finger, shows exactly what is under it.
Set the grid size with the minus and plus buttons next to Rows and Columns. Faint yellow lines inside the outline show where the solver expects each grid line. They should sit on the photo's lines all the way across. If they drift toward one side, a corner is off or the count is wrong.
Tap Find dots. The solver straightens the board and reads every cell.
Check the straightened crop by switching to Original above the board. It should look flat and square-on, with evenly spaced lines. If it looks skewed, tap Adjust outline, fix the corners and tap Find dots again before you edit anything, because reading the image again replaces your edits.

On a computer, you can press Tab to select a handle and move it with the arrow keys. Hold Shift for bigger steps. If two handles cross, you'll see Corners must form a convex board outline in clockwise order. Put each one back on its own corner, in the order top left, top right, bottom right, bottom left.

Then compare the board with your game, dot by dot, using Fixing detection mistakes.