Converting JPEG to WEBP increases the size of the photo

[4Marvin2]

Hi, I am trying to use imagick to convert photos and it works great. But when I try to convert big photos larger than 10MB, the size of the resulting photo is larger than the original photo.

My code:

imagick.Initialize()
defer imagick.Terminate()

mw := imagick.NewMagickWand()
defer mw.Destroy()

err := mw.ReadImage("e.jpeg")
fmt.Println(err)

err = mw.WriteImage("e.webp")
fmt.Println(err)

Also I try this:

imagick.Initialize()
defer imagick.Terminate()

mw := imagick.NewMagickWand()
defer mw.Destroy()

err := mw.ReadImage("e.jpeg")
fmt.Println(err)

err = mw.SetImageFormat("webp")
fmt.Println(err)

b := mw.GetImageBlob()

f, err := os.Create("e.webp")
if err != nil {
    log.Fatal(err)
}

_, err = f.Write(b)
if err != nil {
    log.Fatal(err)
}

I use gopkg.in/gographics/imagick.v3/imagick on MacOS Ventura 13.3.1 and gopkg.in/gographics/imagick.v2/imagick on Ubuntu 22.04.2 LTS.

Images that are larger after conversion: https://www.freepik.com/free-photo/galaxy-nature-aesthetic-background-starry-sky-mountain-remixed-media_17226410.htm#query=4k&position=0&from_view=keyword&track=sph

https://www.freepik.com/free-photo/grassy-hills-with-flowers-mountains_9655791.htm#page=4&query=4k&position=4&from_view=keyword&track=sph

Please explain to me, maybe I'm doing something wrong? With image, for example, 5MB size, everything works well.

[justinfx]

You cannot assume that the default settings for an output will always be the best option. The act of converting from jpeg to webp will not guarantee a smaller file unless you select a lossy option for the output file. Consider the following ImageMagick convert command, using your first example image:

$ convert input.jpg output.webp
$ du -h input.jpg output.webp
 17M    input.jpg
 25M    output.webp

With no options provided, the webp ends up larger than the input jpeg.

But if we tell the output to use compression of 50%:

$ convert input.jpg -quality 50 output.webp
$ du -h input.jpg output.webp
 17M    input.jpg
5.2M    output.webp

Stick with your first approach if using Read/Write unless you really need to read the entire blob into memory first, and use SetCompressionQuality

Please also refer here for webp options availabe using SetOption: https://imagemagick.org/script/webp.php

[4Marvin2]

SetImageCompressionQuality seems to be what I need. Now everything works correctly. Thank you!

Do I understand correctly that to convert to webp I need to use SetImageCompressionQuality, and to convert to other formats I need to use SetCompressionQuality?

[justinfx]

Are you saying that using SetCompressionQuality did not work in this case?

If you search the history of the issues on this project you will find similar questions. The SetImage* methods are for applying settings to individual images in the wand. Usually you want the Set* methods to control the output settings.

[4Marvin2]

Yes, I tried to do like this:

err := mw.ReadImage("c.jpeg")
fmt.Println(err)

err = mw.SetCompressionQuality(50)
fmt.Println(err)

err = mw.WriteImage("c.webp")
fmt.Println(err)

And got the result as before.

If I use SetImageCompressionQuality:

err := mw.ReadImage("c.jpeg")
fmt.Println(err)

err = mw.SetImageCompressionQuality(50)
fmt.Println(err)

err = mw.WriteImage("c.webp")
fmt.Println(err)

result is correct.

I found this issue https://github.com/gographics/imagick/issues/204 and if I understood correctly, then SetCompressionQuality does not work for webp.

But maybe I'm doing something wrong?

[justinfx]

Cool. I guess that is specific to the webp delegate implementation. If it works, go with it.