53Pictures
A photo of a worksheet or of last lesson's whiteboard is rarely ready to teach from. It is grey rather than white, lit brightly down one side, shot at an angle, and the writing is a washed-out charcoal instead of black. The image lab is a darkroom built into Slate that fixes exactly that, and it can go further: turn a photograph into a line drawing for the class to colour in, lift a subject off its background, or restyle a picture as a comic, a blueprint or a pencil sketch.
Everything happens on your own device. No picture is uploaded, nothing is sent to a server, and there is no account or sign-in — the same as the rest of Slate. A large photo is worked on at a sensible size so the preview keeps up as you drag a slider.
Getting a picture in
From the boardPaste or add a picture, select it, then tap the image lab button on its action bar. What you place afterwards goes back in the same spot at the same size, and ⌘/Ctrl+Z undoes it like any other change.
On its ownOpen Tools → Image lab with nothing selected. Drop a file onto the panel, paste one straight in with ⌘/Ctrl+V, or choose a file. Useful when you only want a PNG to send to someone.
FinishingPlace on board puts the result on the board; Download saves it instead. Reset throws away every adjustment and shows the picture exactly as it arrived, however far you have wandered. Cancel leaves the board untouched.
Start from a workflow
Twenty-three starting points, grouped by what you are trying to do. Each one sets a dozen or so controls at once, and for most jobs picking the right one is the whole task.
Clean up a photoWhiteboard turns a photo of a board into dark ink on white paper, evening out the lighting and taking down camera glare. Document flattens and sharpens a page of writing. Marker does the whiteboard job but keeps the marker colours. Receipt rescues faint thermal print. Photo tidy is a gentle all-round correction — white balance, levels, a little local contrast. Cut out drops the background away to transparency. On white puts the subject on clean white paper.
Line drawingsBalanced is the safe first try — even outlines, most noise gone. Clean lines keeps fewer, bolder lines. Fine detail keeps everything and smooths nothing. Portrait is kinder to faces. Pencil gives a soft graphite sketch, Ink wash brushy ink outlines, Etching a crosshatched engraving, and Blueprint white lines on deep blue. These are the ones to reach for when you want a colouring sheet or a diagram to trace.
StyliseComic (bold halftone dots), Cartoon (flat cel shading with an outline), Pop art (few colours, high punch), Newsprint (dithered like old newspaper), Painterly and Oil paint (soft and thick brushed colour), Pixel art, and ASCII, which rebuilds the picture out of letters.
Adjust, when a workflow is nearly right
Sixty-five controls sit under Adjust, in seven groups. Only the ones the chosen effect actually uses are shown, so the list stays short instead of burying the three that matter.
Lighting & inkEven out lighting removes the bright-one-side look of a photo taken under a window, and Lighting detail sets how local that correction is. Take down glare handles the hotspot where a flash or a lamp bounced off the board. Ink, Paper point and Ink strength decide how far the writing is pushed to black and the paper to white — keeping marker colours, or forcing everything to mono.
Straighten & cropStraighten rotates by a fraction of a degree to level the writing. Perspective squares up a page shot from an angle. Crop trims each edge as a percentage, Turn rotates in quarters, and Flip mirrors across or over.
ColourBrightness, Warmth and Tint for a photo shot under the wrong light; Colour and Vibrance for how strong the colours read; Shadows and Highlights to open up the dark or pull back the bright; Auto white balance to let Slate judge it.
Sharpen & cleanSharpen for soft handwriting, Local contrast to make faint pencil readable, Smooth to quiet camera noise without losing edges, plus Midtones, Contrast and Auto levels.
BackgroundFind the background by its corners, by a colour you pick, or by whether it is light or dark, then replace it with transparency, white, black, a colour of your own, or a blur. How fussy, Soften edge and Pull in edge tidy the cut, and Show the cut-out displays the mask itself so you can see what is being kept.
EffectTwenty effects, from edge finders (Canny, Sobel, XDoG, Sketch) through thresholds for text (Threshold, Adaptive) to Posterise, Cel, Duotone, Kuwahara, Oil, Halftone, two dithers, Crosshatch, Stipple, Pixelate, Emboss and ASCII — each with only its own settings on show.
FinishVignette and Grain for atmosphere, and a Border in any colour. Invert and Transparent flip a line drawing to white-on-black or drop the paper entirely — handy for laying ink over a dark board.
Checking your work
Before / after splitTick Before / after split under the picture and the left half shows the original while the right half shows the result, with a line down the middle. It is the quickest way to tell whether a pass has actually improved the writing or merely lightened everything.
Size & timingThe size of the result and how long the last pass took are shown beside the title, along with a figure for the effect where one makes sense — how much of the picture ended up as ink, how many dots a halftone used, how many letters an ASCII rendering needed.
Good to knowThe lab loads the first time you open it rather than with the page, so it costs nothing until you want it — and it is stored for offline use, so the first time works with no connection too. Results are saved in whichever format is genuinely smaller for that picture: a cleaned page of writing packs down far better as a PNG, a tidied photograph as a JPEG, and anything with transparency stays a PNG because it has to.
Part of the Slate guide — or read the whole guide on one page.