Appearance

Resize Node ​

Purpose & Use Cases ​

The resize node provides high-performance image scaling with flexible dimension control and automatic aspect ratio preservation. It supports both fixed dimensions and proportional scaling using optimized C++ backend processing.

Real-World Applications:

  • Web Image Optimization: Scale images for different device sizes and bandwidths
  • Thumbnail Generation: Create preview images and gallery thumbnails
  • Print Preparation: Resize images to specific print dimensions
  • Storage Optimization: Reduce image sizes to save storage space
  • Performance Enhancement: Optimize image sizes for faster loading

/flows/node-red-contrib-rosepetal-image-tools/assets/nodes/transform/resize-demo.gif

Input/Output Specification ​

Inputs ​

  • Single Image: Standard image object format
  • Image Array: Array of image objects for batch processing
  • Dynamic Dimensions: Dimensions can be provided via message properties

Input Image Format ​

javascript
{
  data: Buffer,        // Raw pixel data
  width: number,       // Original width in pixels
  height: number,      // Original height in pixels
  channels: number,    // Channel count (1, 3, 4)
  colorSpace: string,  // "GRAY", "RGB", "RGBA"
  dtype: string        // "uint8"
}

Outputs ​

Output format depends on the Output Format setting:

  • Raw: Standard image object (fastest for processing chains)
  • JPEG/PNG/WebP: Encoded file buffer ready for storage/transmission

Configuration Options ​

Input/Output Paths ​

  • Input From: msg.payload (default), flow.*, global.*
  • Output To: msg.payload (default), flow.*, global.*
  • Purpose: Flexible data routing for complex workflows

Dimension Configuration ​

Width Settings ​

  • Mode:
    • Set to: Fixed pixel value (e.g., 800 pixels)
    • Multiply by: Scale factor (e.g., 0.5 for half size)
  • Value Sources:
    • Number: Fixed value
    • msg.*: Dynamic from message property
    • flow.*: From flow context
    • global.*: From global context
  • Auto Mode: Leave empty for automatic aspect ratio preservation

Height Settings ​

  • Mode: Same options as width (Set to / Multiply by)
  • Value Sources: Same dynamic options as width
  • Auto Mode: Leave empty for proportional scaling

Output Format Options ​

Raw Format (Default) ​

  • Performance: Fastest option for processing chains
  • Use Case: When passing to other transform nodes

JPEG Format ​

  • Quality: 1-100 (default: 90)
  • Use Case: Final output, web optimization
  • Compression: Lossy, smaller file sizes

PNG Format ​

  • Optimize: Checkbox for additional compression
  • Use Case: When transparency needed or lossless required
  • Compression: Lossless

WebP Format ​

  • Quality: 1-100 (default: 90)
  • Use Case: Modern web applications
  • Compression: Superior to JPEG at same quality

Debug Options ​

  • Show Processed Image: Visual preview in Node-RED editor
  • Debug Width: Preview image width in pixels
  • Interactive: Click preview to hide

Performance Notes ​

C++ Backend Optimization ​

  • High-Speed Processing: OpenCV-based scaling algorithms
  • Memory Efficient: Optimized memory management for large images
  • Parallel Processing: Array inputs processed concurrently
  • Algorithm: Uses high-quality interpolation for best results

Processing Modes ​

  • Batch Processing: Arrays processed in parallel for maximum throughput
  • Async Operations: Non-blocking processing with timing display
  • Status Display: Real-time processing time and result information

Real-World Examples ​

Web Image Optimization ​

[Image-In: original.jpg] → [Resize: 800x600] → [Save: web_optimized.jpg]

Create web-optimized versions of high-resolution images.

Responsive Image Set ​

[Image-In] → [Resize: 1200x Auto] → [JPEG Quality 80] → [Large]
          → [Resize: 800x Auto]  → [JPEG Quality 85] → [Medium]
          → [Resize: 400x Auto]  → [JPEG Quality 90] → [Small]

Generate multiple sizes for responsive web design.

Thumbnail Generation ​

[Image Array] → [Resize: 150x150] → [PNG] → [Thumbnail Gallery]

Create square thumbnails from image collections.

Batch Photo Processing ​

[Photo Collection] → [Resize: Multiply 0.7] → [Save Reduced]

Reduce photo sizes by 30% for storage optimization.

Dynamic Sizing ​

[Set msg.targetWidth] → [Resize: Set to msg.targetWidth, Auto height] → [Output]

Resize based on runtime requirements.

Common Issues & Troubleshooting ​

Aspect Ratio Distortion ​

  • Issue: Images appear stretched or squashed
  • Cause: Both width and height set without considering aspect ratio
  • Solution: Leave one dimension empty for auto-calculation

Memory Issues with Large Images ​

  • Issue: Processing very large images causes performance problems
  • Solution: Process in batches or reduce dimensions incrementally
  • Best Practice: Consider source image size vs. target size

Quality vs. File Size Balance ​

  • Issue: Output files too large or quality too low
  • Solution: Adjust quality settings (80-95 for good balance)
  • Format Choice: Use WebP for best compression, PNG for transparency

Dynamic Value Errors ​

  • Issue: Runtime errors when using message properties
  • Solution: Validate dynamic values exist and are valid numbers
  • Debugging: Use debug nodes to verify property values