Add Watermark to Images Securely Online

Adding a watermark to an image requires compositing two raster layers using alpha channel blending mathematics. Khalasna executes this client-side using HTML5 Canvas 2D contexts and globalCompositeOperation settings. When an image and watermark (text or secondary logo) are loaded, the primary image is drawn onto an off-screen canvas at native dimensions. The graphics state is configured with globalAlpha set to your chosen transparency level. For text watermarks, the engine computes text layout bounds, sets font metrics, translates the context origin, and applies a rotation matrix (ctx.rotate) before invoking ctx.fillText(). For logo watermarks, the secondary image is painted using ctx.drawImage() with proportional scaling. The resulting composited pixel matrix blends the watermark seamlessly with underlying photo textures. The final canvas buffer is serialized into JPEG, PNG, or WebP format locally, guaranteeing total privacy for copyrighted creative assets.