QOI

QOI, the Quite OK Image Format, is a simple lossless image format designed around easy implementation and fast encode/decode loops. In ImageSharp, it is a compact option when you want lossless RGB or RGBA output without the broader feature surface of PNG.

ImageSharp exposes QOI-specific APIs through QoiEncoder and QoiMetadata.

Format Characteristics

QOI is best thought of as a small, focused lossless format.

QOI is intentionally simple: it stores RGB or RGBA pixel streams using a compact set of operations that are easy to encode and decode. That simplicity is the appeal. It can be fast and convenient in controlled pipelines where both sides agree to use the format.

The tradeoff is ecosystem breadth. QOI does not carry the same metadata surface as PNG, WebP, or TIFF, and it is not a browser delivery format. Use it when simple lossless interchange is valuable and the producer and consumer are both under your control.

A few practical implications:

• QOI is lossless.
• The format stores image channel count as RGB or RGBA.
• The format stores a simple color-space flag.
• In ImageSharp, Channels and ColorSpace are informative metadata. They do not change how the pixel chunks themselves are encoded.
• QOI has a much smaller ecosystem than PNG or WebP.

Save as QOI

Use QoiEncoder when you want QOI output:

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Qoi;

using Image image = Image.Load("input.png");

image.Save("output.qoi", new QoiEncoder
{
    Channels = QoiChannels.Rgba,
    ColorSpace = QoiColorSpace.SrgbWithLinearAlpha
});

Key QOI Metadata

The most useful QOI-specific values are:

• Channels, which records whether the image is RGB or RGBA.
• ColorSpace, which records whether the image is tagged as sRGB with linear alpha or all-channels-linear.

Those values describe how consumers should interpret the stored pixel stream. They are not a substitute for full color-management metadata, so QOI is usually a poor choice when ICC workflows or rich metadata are part of the contract.

Read QOI Metadata

Use GetQoiMetadata() to inspect QOI-specific metadata:

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Qoi;

using Image image = Image.Load("input.qoi");

QoiMetadata qoiMetadata = image.Metadata.GetQoiMetadata();

Console.WriteLine(qoiMetadata.Channels);
Console.WriteLine(qoiMetadata.ColorSpace);

When to Use QOI

QOI is usually worth considering when:

• You want a simple lossless format in a controlled pipeline.
• Fast, straightforward encoding and decoding matters more than ecosystem breadth.

QOI is usually a poor fit when:

• You need broad browser or tool compatibility.
• You need richer metadata or more mature ecosystem support.

For wider compatibility, PNG and WebP are usually better starting points.

Practical Guidance

• Use QOI in controlled pipelines where both producer and consumer agree on the format.
• Prefer PNG or WebP when files need to be opened broadly by browsers, design tools, or operating systems.
• Treat QOI as an interchange or internal-storage choice, not a general publishing format.
• Test size and speed against representative data; simple formats are not automatically smaller for every image.