1. Open your image. Click Import Schematic in the left panel, or Select Source Asset in the middle of the canvas. PNG, JPG and WEBP files up to 50 MB work. A clear, high-resolution image gives the neatest result.
2. Pick a wire colour. Choose one of the eleven preset colours, or use the colour picker for your own. Decide what each colour means before you start (see the next section).
3. Set the thickness. Use the slider or type a number from 1 to 50 pixels. The thickness is in pixels of the original image, so a large image needs a thicker wire to stay visible.
4. Choose how wires bend. PCB (90°) keeps every segment horizontal or vertical; Direct lets you draw at any angle. Then choose Smooth (rounded corners) or Rigid (sharp corners).
5. Draw. With the Wire tool selected, click once to start a wire and click again at each corner. Double-click to finish that wire. Start the next wire with a new click.
6. Fix mistakes. Press Ctrl + Z (or Cmd + Z on a Mac) to undo the last step. Switch to the Eraser and click a wire to remove just that wire. Clear All removes every wire.
7. Save it. Click Export Schematic. You get a PNG with exactly the same width and height as your original image, with the wires drawn into it.

Give every colour one meaning

An annotation is only useful if a reader can decode it without asking you. Pick a small set of colours, give each one a job, and write the key somewhere on the image or in your report. A common choice follows the colours used for real wires on a workbench:

Colour	Typical meaning
Red	Positive supply: the 5 V, 3.3 V or battery rail
Black or dark blue	Ground (0 V), the return path for every current
Yellow or orange	A clock or a fast signal you want to follow
Green	Data lines, such as I2C SDA or a UART transmit line
Cyan or white	The one path you are explaining right now

The exact choice matters less than being consistent. If red means the 3.3 V rail in one figure, it should mean the same in every figure of the report.

Choosing a thickness

Wire thickness is measured in pixels of the original image, not of your screen. On a 1000-pixel-wide screenshot, 3 to 5 pixels is usually enough. On a 4000-pixel scan, the same wire would look like a hair, so use 10 to 16 pixels. Zoom out to see the whole image at the size a reader will see it, and check the wire is still easy to follow.

PCB (90°) or Direct

Schematic diagrams are drawn with horizontal and vertical wires, so PCB (90°) mode matches them: each new point snaps so the segment is straight across or straight down. Use it to trace along the existing wires of a schematic. Direct mode follows your clicks at any angle, which suits photos of breadboards, hand-drawn diagrams and arrows pointing at a part.

Smooth or Rigid

Smooth rounds each corner with a short curve, which is easier on the eye in slides and tutorials. Rigid keeps sharp corners, which looks closer to real copper traces and to printed schematics. Both export at full resolution.

Action	How
Add a point to the current wire	Click on the canvas
Finish the current wire	Double-click
Undo the last step	Ctrl + Z (Cmd + Z on a Mac), or the Undo button
Zoom in and out	Scroll wheel over the canvas
Move around the image	Hold Space or Alt and drag, or drag with the middle mouse button
Remove one wire	Eraser tool, then click the wire

SchemFlow is designed for a mouse or trackpad on a laptop or desktop. On a phone the canvas is small and a finger covers the point you are placing, so precise work is much easier on a bigger screen.

A schematic shows how parts are connected, not where they sit on the board. Before you trace anything, it helps to know what the lines and labels mean.

• A wire is a connection. Every point along one line is at the same voltage. The whole set of points joined together is called a net.
• A dot means joined; no dot means crossing. Where two lines meet with a filled dot, they are connected. Where they cross with no dot, they pass over each other without touching. This is the most common reading mistake for beginners.
• Labels can replace wires. Two wires ending in the same net label, such as SDA or VCC, are connected even though no line joins them. Power and ground symbols work the same way: every ground symbol on the page is one net.
• Reference designators name each part. R is a resistor, C a capacitor, L an inductor, D a diode, Q a transistor and U an integrated circuit. R4 is simply the fourth resistor.
• Pin numbers matter. The small numbers beside a chip's pins match the pin numbers in its datasheet. Tracing a signal usually means following it from one numbered pin to another.

A good first exercise: open the application circuit from a sensor's datasheet and trace its power pins in red, its ground in black, and its data lines in green. By the end you will know exactly what that sensor needs to work.

• Lab records and project reports. Highlight the path a signal takes through the circuit, so the examiner can follow your explanation without hunting.
• Debugging a board. Mark each connection in green once you have checked it with a multimeter's continuity mode. The unmarked wires are the ones left to test.
• Recording a modification. If you cut a trace or add a wire to a board, draw the change on a photo of it, so the next person knows the board differs from its schematic.
• Teaching. Trace one idea at a time: first the power rails, then the clock, then the data. Export one image per step and put them on successive slides.
• Asking for help. A photo with the suspect wires marked gets a far better answer on a forum than a paragraph describing them.

• Start sharp. Annotations cannot make a blurry image clearer. When taking a schematic from a PDF, zoom the PDF in until the lines are crisp before you take the screenshot.
• Prefer PNG to JPG. JPG compression smudges thin lines and text. If you must use a photo, take it square-on in good light.
• Crop first. Cut the image down to the part of the circuit you are explaining. A smaller image is faster to work on and easier for the reader.
• Export is full size. The PNG has the same pixel dimensions as the image you opened, so it stays sharp when printed or zoomed.
• Your file stays with you. The picture is read by your browser and never sent to a server. Closing the tab discards it, so export before you leave.

Which image formats can I open?

PNG, JPG and WEBP, up to 50 MB. The export is always a PNG.

Will the exported image be smaller than my original?

No. It has exactly the same width and height in pixels, with the wires drawn on top.

Can I edit a wire after finishing it?

Not point by point. Undo it, or erase it with the Eraser tool and draw it again.

Does it work with KiCad or other design tools?

SchemFlow works on images, so it accepts an export or screenshot from any tool. It does not read design files, and it does not change your design - it only adds a drawing layer on a picture.

Is my schematic uploaded anywhere?

No. It is processed entirely inside your browser.