---
title: "Convert PNG to JPG in C#"
url: https://recursiveai.org/oneimage/cookbook/convert-png-to-jpg/
description: "Convert PNG to JPG in C#, keeping transparent areas white, and JPG to PNG, BMP, TIFF, GIF or ICO: the file extension picks the format. Runnable code with OneImage, on any OS."
version: "1.10.4"
---

# Convert PNG to JPG in C#

Load the PNG, put it on a background with `Flatten` (JPEG has no transparency), and save it with a `.jpg` extension. The extension picks the output format, so the same two lines convert between PNG, JPEG, WebP, GIF, TIFF, BMP and ICO in any direction. The program below converts a transparent PNG logo.

```shell
dotnet new console -o ConvertImage && cd ConvertImage
dotnet add package RecursiveAI.OneImage --version 1.10.4
curl -L -o logo.png https://recursiveai.org/assets/brand/icon-512.png
```

OneImage needs the .NET 10 SDK. Put this in `Program.cs` and run `dotnet run`:

```csharp
using OneImage;

Image png = Image.Load("logo.png");

// JPEG can't store transparency: put the logo on white, then save at quality 90.
png.Flatten(new Rgba32(255, 255, 255, 255))
   .Save("logo.jpg", new SaveOptions
   {
       EncoderOptions = new JpegEncoderOptions { Quality = 90 },
   });

// Any other direction is a load and a save; the extension picks the encoder.
Image.Load("logo.jpg").Save("logo-from-jpg.png");
png.Save("logo.bmp");
png.Resize(width: 64).Save("favicon.ico");

string[] files =
    ["logo.png", "logo.jpg", "logo-from-jpg.png", "logo.bmp", "favicon.ico"];
foreach (string file in files)
{
    ImageInfo info = Image.Identify(file);
    long kb = new FileInfo(file).Length / 1024;
    string size = $"{info.Width}x{info.Height}";
    Console.WriteLine($"{file}: {info.Format.Name} {size}, {kb} KB");
}
```

```text
logo.png: png 512x512, 7 KB
logo.jpg: jpeg 512x512, 8 KB
logo-from-jpg.png: png 512x512, 17 KB
logo.bmp: bmp 512x512, 1024 KB
favicon.ico: ico 64x64, 16 KB
```

The input format is detected from the file’s content, not its name, so a PNG saved as `photo.jpg` still loads. Without `Flatten`, the JPEG encoder writes whatever color values the transparent pixels store, which is often black.

## Convert to a stream

A stream has no extension, so name the format with its `Instance`:

```csharp
using OneImage;

using var output = new MemoryStream();
Image.Load("logo.png")
     .Flatten(new Rgba32(255, 255, 255, 255))
     .Save(output, JpegFormat.Instance);
Console.WriteLine($"{output.Length} bytes of JPEG in memory");
```

```text
6858 bytes of JPEG in memory
```

The format instances are `PngFormat`, `JpegFormat`, `WebPFormat`, `GifFormat`, `TiffFormat`, `BmpFormat` and `IcoFormat`. `SaveAsync` does the same for ASP.NET Core responses.

## Limits

- **JPEG is lossy** and has no alpha channel. Converting JPEG to PNG makes a larger file, not a better image.
- **JPEG and BMP hold one image.** Saving an animated GIF or multipage TIFF as JPEG writes the first frame; see [Split a multipage TIFF](https://recursiveai.org/oneimage/cookbook/split-multipage-tiff/).
- **ICO** entries are at most 256×256, so resize first.
- **Metadata is kept** by a plain load and save, including any EXIF GPS position. See [Remove EXIF metadata](https://recursiveai.org/oneimage/cookbook/remove-exif-metadata/).
- **Not supported:** HEIC and AVIF. SVG, PSD and PDF need their add-on packages ([SVG to PNG](https://recursiveai.org/oneimage/cookbook/svg-to-png/), [PSD to PNG](https://recursiveai.org/oneimage/cookbook/psd-to-png/), [PDF to image](https://recursiveai.org/oneimage/cookbook/pdf-to-image/)).

For web output, [WebP](https://recursiveai.org/oneimage/cookbook/convert-to-webp/) is usually smaller than JPEG. Every encoder option is in the [guide](https://recursiveai.org/oneimage/docs/guide/#saving).