Image SDR → HDR Conversion, Online & Free

1. Select Image

Click to select, drag, or paste an image

Supports JPG, PNG, WEBP, GIF, and other formats

Output

AVIF Encoding Options

Bit Depth

10-bit has the best compatibility; 12-bit has slightly higher quality but poorer browser support.

YUV Subsampling

4:4:4 retains full chroma information; 4:2:0 results in smaller files and saves bandwidth.

Speed

Encoding speed: 0 is slowest/highest quality, 10 is fastest/lowest quality. Recommended 5–7.

Lossless

Lossless mode ignores Q values, often used for archiving, not recommended for web distribution.

Advanced Settings (Brightness, Dithering, Quantization, etc.)

Quantizer

minQmaxQ

Quantizer determines compression ratio and quality; smaller values mean higher quality.

Controls lossy compression quality. Lower values mean higher quality. Recommended min/max≈0/4 for high-quality HDR.

Brightness Mapping (iTMO)

knee

The 'knee' point of the brightness curve, which determines where stronger highlight enhancement begins.

0.80

midGain

Mid-tone/SDR white point (100 nits) gain; 2.5× is roughly 250 nits.

2.60

hiGain

Theoretical maximum brightness gain; 8× is roughly 800 nits.

10.50

shoulder

Smoothness of the highlight transition zone; larger values result in a 'harder' shoulder.

1.50

Dithering & Debugging

Enable 8-bit Dithering

Adds a small amount of dithering before 8-bit quantization, which can effectively reduce banding. It also helps with 10-bit output.

Dither Amp

Dither strength; 0.5–1.0 is recommended.

0.75

Experimental Features
These features change the visual appearance. They are off by default and do not affect the existing effect. It's recommended to use them in conjunction with the preview for comparison.

Darker Shadows (Shadow Toe)

Applies a 'Toe' curve to low brightness areas to enhance black levels and contrast, while avoiding crushed details.

Toe Start0.08

Toe Strength0.20

Color Space Expansion

Expands the chroma components in linear Rec.2020 to increase saturation; CICP maintains BT.2020 + PQ.

Saturation Boost0.15

HDR Output Only (Do not generate SDR fallback image)

The left side of the preview uses your original image as the SDR reference; if your device doesn't support HDR, the right side will fall back to the original image.

Quick Mode

Increases encoding speed by: raising 'speed', using YUV 4:2:0, fixing 10-bit, disabling lossless, increasing the Q range, and forcing HDR-only. Suitable for large images or restricted environments, but image quality may be slightly reduced.

Example Preview (Left: Original, Right: Converted)SDR Display

Original

Converted

Example Parameters

{
  "outFormat": "avif",
  "avifDepth": 10,
  "yuv": "444",
  "lossless": false,
  "speed": 6,
  "dither8": true,
  "ditherAmp": 0.75,
  "minQ": 0,
  "maxQ": 4,
  "hdrOnly": false,
  "itmo": {
    "knee": 0.8,
    "midGain": 2.6,
    "hiGain": 10.5,
    "shoulder": 1.5
  },
  "experimental": {
    "enableToe": true,
    "toeStart": 0.08,
    "toeStrength": 0.2,
    "enableGamut": true,
    "satBoost": 0.15
  }
}

Important Note on Conversion Quality

Please understand that 'up-converting' an SDR image to HDR with this tool is fundamentally different from a native HDR photo taken directly with a camera. SDR images have permanently lost details in extreme highlights and shadows during compression, and even by extending the brightness range, textures cannot be magically restored.

For more precise local control, it is recommended to use professional post-processing tools.

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Afdian Solana