What is Alpha Channel?

Alpha Channel — Image Transparency Explained

An alpha channel stores transparency information for each pixel in an image, with values ranging from fully transparent to fully opaque. It is the fourth channel in RGBA color, enabling smooth blending of images over backgrounds.

Détail technique

Alpha values are typically stored as 8-bit (0-255) or floating point (0.0-1.0) per pixel. Pre-multiplied alpha multiplies color values by opacity for faster compositing, while straight alpha stores them independently.

Exemple

```javascript
// Convert RGB to HSL
function rgbToHsl(r, g, b) {
  r /= 255; g /= 255; b /= 255;
  const max = Math.max(r, g, b), min = Math.min(r, g, b);
  const l = (max + min) / 2;
  let h = 0, s = 0;
  if (max !== min) {
    const d = max - min;
    s = l > 0.5 ? d/(2-max-min) : d/(max+min);
  }
  return [h, s, l];
}
```

Outils associés

C Compress Image R Resize Image C Crop Image R Rotate Image F Flip Image C Convert Image W Watermark Image S SVG to PNG I Image to Base64 R Round Corners A Add Border I Image Filters A Adjust Image B Blur Image S Sharpen Image M Make Square G Grayscale Image S Sepia Image P Pixelate Image S Strip Image Metadata

Termes associés

Channel Aspect Ratio AVIF Chroma Subsampling Chromatic Aberration Color Grading (Image) Compression Artifact Dithering (Image) Image Histogram Image Registration Metadata Resolution Alpha Compositing Image Pyramid Rasterization Bit Depth Color Space Lossy Compression HDR Raster Graphics Vector Graphics Sprite Sheet Thumbnail WebP Crop Image Optimization Resize ICC Profile Image Interpolation Canvas Convolution DPI/PPI Gamma Histogram Noise Reduction (Image) Panorama Stitching Feature Matching Image Segmentation Object Detection Mipmap Morphological Operations Texture Atlas Gamut Mapping IPTC Tone Mapping Focus Stacking Vignetting XMP Batch Resize Content-Aware Fill Lossless Compression EXIF Color Profile DPI