Clearly mark known specifications with multiple dimension lines without inferring real-world lengths from pixels.
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Image Dimension Annotator User Guide
Locally load one JPG or PNG, create multiple dimension lines from two endpoints, enter known values and units manually, adjust arrows, labels, and lines, then export an annotated PNG at the source resolution.
How to use
Load one static JPG or PNG and verify its decoded dimensions after EXIF orientation normalization.
Choose Add dimension line and place two endpoints on the image in sequence. Then enter the known value and unit manually, choose closed arrows, open arrows, or ticks, and place the label above, in the middle, or below the line.
Finish the layout with selection, endpoint dragging, keyboard nudging, zoom, pan, show/hide, and undo/redo. Export the PNG after every visible dimension line is valid.
Formats and limits
One static JPG or PNG at a time, up to 20 MiB, 12 million pixels, and 8,192 px per side. One image may have up to 50 dimension lines, and zoom affects the editing preview only.
Values must be entered manually, with up to 10 integer digits and 4 decimal places. Units may contain up to 12 characters without whitespace or HTML special characters. The tool does not automatically measure real-world length from pixels, DPI, scale, or perspective.
Above and below labels use a stable direction rule and do not flip sides when endpoints are exchanged. Output is drawn with browser fonts and Canvas, so glyphs or antialiasing may differ from other layout software.
Output
A new flattened PNG at the EXIF-normalized source width and height. The source file is not modified, editable layers and annotation data are not retained, and leaving the page clears the session.
Frequently asked questions
Does the dimension line automatically convert its length to millimeters?
No. The line only determines the annotation position and direction; its text comes entirely from the value and unit you enter. The tool has no scale and performs no measurement or compliance assessment.
Will an above label move to the opposite side after swapping the endpoints?
No. The tool uses a stable direction independent of endpoint order, so above, middle, and below remain visually consistent after endpoints are exchanged.
The file name and content are only processed in your browser and are not transmitted to the server. The original file will not be overwritten. Please export the required results before leaving the tool.