Annotateur d'Images

Image annotation is the process of adding visual marks to an image -- arrows, rectangles, circles, text labels, highlights, and blurs -- to draw attention to specific areas or convey additional information. Common use cases include: software tutorials (highlighting buttons and menu items with arrows and labels), design feedback (circling issues and adding comments), bug reports (annotating screenshots with steps to reproduce), and privacy redaction (blurring faces, license plates, or sensitive text).

The technical implementation uses the Canvas API's 2D drawing context. Rectangles are drawn with strokeRect() and fillRect(). Circles and arrows use arc() and lineTo() with stroke(). Text is rendered with fillText() and strokeText(). Highlights use a semi-transparent fill color. Blurring is achieved by drawing the selected region at reduced resolution and scaling it back up, or by applying a CSS filter: blur() to a clipped region. Each annotation is stored as an object in an array, allowing undo/redo and re-rendering.

For privacy redaction, blurring is preferable to solid-color covering because it preserves some visual context (you can still tell there's text or a face) while making the content unreadable. However, blurring is not cryptographically secure -- sophisticated algorithms can sometimes recover blurred text. For truly sensitive information (passwords, Social Security numbers), use solid black rectangles instead of blurs. The blur strength (radius) should be at least 10-15 pixels to prevent recovery.

Use consistent colors for different types of annotations: red for errors or problems, green for correct items, blue for information, yellow for highlights. Keep annotations minimal -- too many marks on an image create visual noise and reduce clarity. Use arrows to point to specific elements rather than circling large areas. Label each annotation with a number or short text so the viewer can follow the sequence.

When creating tutorials, annotate screenshots in the order of the steps. Use callout boxes (text on a colored background with an arrow pointing to the relevant area) for step-by-step instructions. Export the annotated image as PNG (not JPEG) to avoid compression artifacts around text and sharp lines. If the annotated image will be displayed on a high-DPI screen, render at 2x resolution and scale down with CSS for crisp text and lines.