Compare two images side by side with difference highlighting and slider comparison. Perfect for quality comparison and before/after effect comparison.
Features
- Multiple Compare Modes: Supports side-by-side and slider comparison modes to meet different comparison needs
- Difference Highlight Display: Automatically detect and highlight difference areas between two images, intuitively display difference locations
- Interactive Slider: In slider comparison mode, drag slider to view different areas for precise detail comparison
- Precise Pixel Detection: Uses pixel-level comparison algorithm to precisely detect image differences, supports custom difference threshold
Usage Guide
- Step 1: Upload two images to compare.
- Step 2: Select compare mode (side-by-side or slider) and enable difference highlight (optional).
- Step 3: View comparison results, adjust slider position or difference threshold for best comparison effect.
Technical Details
Image Comparison Principle
Image comparison detects differences between two images at pixel level. Side-by-side comparison: display two images side by side for intuitive comparison; slider comparison: use slider to control display area, drag left/right to view different parts; difference highlighting: calculate pixel differences between two images, highlight difference areas in red. Uses Canvas API's getImageData() to get pixel data, compare RGB values pixel by pixel, calculate difference and visualize.
Pixel Difference Detection
Implementation: load two images to Canvas → getImageData() to get pixel data → compare RGB values pixel by pixel → calculate difference (|R1-R2|+|G1-G2|+|B1-B2|) → mark as difference if exceeds threshold → generate difference image (red highlight for difference areas). Supports: custom difference threshold, real-time preview, slider interaction, side-by-side display, etc.
Creative and Practical Scenarios
Image comparison is used for: design review (compare design mockup and implementation), quality check (compare original and compressed images), before/after comparison (compare effects before and after processing), version comparison (compare different versions of images), test verification (compare expected and actual results), learning research (compare effects of different parameters). Helps quickly discover image differences and perform quality assessment, a practical tool for image processing.
Frequently Asked Questions
- What compare modes are available?
- The tool provides two compare modes: side-by-side (display two images side by side for overall comparison) and slider (use slider to control display area, drag to view different parts). Slider mode is suitable for scenarios requiring precise detail comparison.
- How does difference highlighting work?
- Difference highlighting compares two images at pixel level, calculating RGB difference value for each pixel. When difference exceeds the set threshold, that area is highlighted in red. You can adjust the difference threshold to control highlight sensitivity.
- Can I compare images of different sizes?
- Yes, the tool automatically handles images of different sizes. For difference detection, it uses the larger image's size as reference, smaller images are displayed proportionally.
- How to use slider comparison?
- In slider comparison mode, drag the middle slider to control display area. Left side of slider shows first image, right side shows second image. Drag slider to precisely compare details of different areas.
- How to set difference threshold?
- Difference threshold controls sensitivity of difference detection. Lower threshold detects subtle differences more easily; higher threshold only shows obvious differences. Recommended to adjust based on actual needs, generally set between 20-50.
Related Documentation
- MDN - Canvas API - HTML5 Canvas API for image manipulation and processing
- MDN - ImageData API - Canvas ImageData interface documentation
- Web.dev - Image Optimization - Best practices for optimizing images on the web