When dealing with images, we may have to do several format conversions. Depending on the situation, it can be a JPG to PNG conversion, PNG to SVG conversion, or anything. ImageMagick is a tool that supports most of these image format conversions along with the other operations like resizing, reducing the size, changing color scheme ..etc. In this tutorial, we will see how to convert a PNG file to a JPG file. Also, we’ll check how to perform this image conversion as a batch job.

TL;DR: convert image.png image.jpg (ImageMagick 6) or magick image.png image.jpg (ImageMagick 7). Add -quality 85 to control file size, and -background white -flatten -alpha off if the PNG has transparency.

Before jumping to the details, let’s get familiar with the terms used here, ie, JPG, PNG, and ImageMagick. If you are already familiar with these, you can directly skip to the conversion part.

PNG Image Format

PNG (Portable Network Graphics) a raster image format. Raster images use a lossless image compression algorithm. In PNG format, the image will be represented as a collection of interconnected points. The quality of the image will remain unaffected on resizing.

PNG format is best for simple icons & shapes

PNG format can be used for any image files. However, it is more suitable for icons, symbols, or small shapes which does not require a lot of points to represent. It will consume more space for complex images like photographs. So, it is better to convert complex images into other formats like JPG when we are using it on the Web.

JPG Image Format

JPG or JPEG (Joint Photographic Experts Group) is a commonly used lossy compression approach for digital photographs. It allows adjusting the compression ratio with a tradeoff between compression and quality of the image.

JPG format is good for complex shapes

With JPG format, the quality of the image reduces with compression ratio. More compression implies, less quality and less storage space requirement. This format is used for embedding photographs or complex images on websites.

ImageMagick

ImageMagick is an open-source tool that provides advanced image manipulation functionalities to create, edit and convert images. It supports more than 200 types of image formats. ImageMagick facilitates resize, flip, rotate, distort, shear, and transform images. It also helps to apply special effects.

Commonly, ImageMagick is used as a command-line tool, which makes it suitable for batch operations. There are many GUI clients which use ImageMagick underhood for performing image manipulation operations.

How to perform PNG to JPG conversion using ImageMagick?

Now, we are familiar with PNG, JPG, and ImageMagick. So, it is time to talk about the actual topic. How to perform PNG to JPG conversion.

ImageMagick provides a set of command-line tools for performing image manipulation operations. convert is one such tool in the ImageMagick tool suite, that facilitates the conversion of images between various formats. It also provides options to resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.

You can read the complete convert tool documentation using the man pages. The man page for convert can be read using the following commands:

$ convert --help
   OR
$ man convert

The image format conversion can be done using the following command:

$ convert [original image] [converted image name]

This command can be used to convert between any valid image formats.

Note (ImageMagick 7+): Most current Linux distributions ship ImageMagick 7, where the standalone convert binary is deprecated in favor of the magick command. You’ll see a deprecation warning if you run convert directly on IM7. The syntax is otherwise identical — just replace convert with magick:

$ magick [original image] [converted image name]

All the examples below work the same way with magick instead of convert.

Controlling output quality and file size

JPG is a lossy format, so you can trade off file size against image quality using the -quality flag (0-100, higher means better quality and larger file size). This is especially useful when converting photographs for the web:

$ convert original-image.png -quality 85 new-image.jpg

A lower value like 60-70 gives a noticeably smaller file, while 85-95 keeps quality close to the original with a moderate size reduction.

If we want to convert multiple jobs at once, we may use a simple batch job as follows:

for image in *.png ; 
do 
    convert "$image" "${image%.*}.jpg" ;
done

In one line, it can be written like,

$ for image in *.png ;  do convert "$image" "${image%.*}.jpg" ; done

Alternatively, ImageMagick’s mogrify tool can batch-convert an entire directory in place without needing a loop:

$ mogrify -format jpg *.png

This creates a .jpg copy of every PNG in the current directory, leaving the original PNG files untouched.

How to convert PNG to JPG by specifying background color?

In some scenarios, PNG images will be coming with transparent background. If we convert those images directly to JPG, it is likely to cause some unexpected results. In such cases, we can specify the background color, so that, the transparency will be replaced with the specific background color.

For converting a single image with background color,

convert original-image.png -background white -flatten -alpha off new-image.jpg

For converting multiple image files with background color,

for image in *.png ;  do convert "$image" -background white -flatten -alpha off  "${image%.*}.jpg"; done

How to convert from any image format to any other image format?

The convert tool provided by ImageMagick can convert from any image format to any other image format. The above example showcases, how to convert a PNG image to a JPG image.

In general, we can perform the image conversion like,

$ convert <source image name & format> <destination image name & format>
# example
$ convert sample.png sample.webp

Frequently Asked Questions

Does converting PNG to JPG reduce image quality? Yes, potentially. JPG uses lossy compression, so some detail is discarded during conversion. You can minimize the loss by using a high -quality value (85-95).

How do I convert PNG to JPG without losing quality? You can’t fully avoid it since JPG is inherently lossy, but setting -quality 95 or higher keeps the loss visually negligible for most images.

Why does my converted JPG have a black or white background instead of transparency? JPG doesn’t support transparency. Any transparent areas in the source PNG get filled with a background color (black, by default, in some tools). Use the -background white -flatten -alpha off flags shown above to control that color explicitly.

Can I convert PNG to JPG on Windows or macOS with ImageMagick? Yes. ImageMagick is cross-platform - the same convert/magick commands work on Windows and macOS after installing ImageMagick, though batch loops should use PowerShell or a shell like zsh/bash accordingly.

That’s all for now. This post is inspired by an answer given in superuser - an affiliate of StackExange.

In case of any issues, or clarification please let me know via the comment box below.

You may also read, tutorial on converting jpg images to png