[5.x] Media Cache thumbnails

[brianteeman]

Steps to reproduce the issue

Add some png and jpg images to the /images folder

Go to the Filesystem local plugin and enable cache

Compare the file sizes in /images and /media/cache/com_media/thumbs

Expected result

ALL the files in the cache have been reduced in both dimension and filesize

Actual result

All the file dimensions have been reduced but the filesize has in some cases increased

System information (as much as possible)

I have prepared a zip containing 5 images so that we can compare with the same image

filename	original filesize kb	cache filesize kb	reduced
image1.png	44.05	105.85	❌
image2.png	452.83	75.3	✔️
image3.png	30.47	93.39	❌
image4.jpg	250.94	27.79	✔️
image5.jpg	114.55	26	✔️
image6.jpg	260.38	34.84	✔️

Test Images

test.zip

Comments

I appreciate that the original images might have been saved with different compression algorithms and ratios. These are just a random selection of images on my hdd.

In all cases the file has been reduced in dimensions so at the very least it would be reasonable to assume that its a bug if the reduced file is double the storage size of the original

[Fedik]

It kind of expected, for PNG.
It not a bug.
I would say: it is how algorithm work for PNG.

In theory we can try to play with higher compression, but still, in some cases PNG can be bigger.

[brianteeman]

How can it be expected to reduce the dimensions of a png and yet the filesize increases by 300%

That completely defeats the objective of the thumbnail creation

/me doesnt understand how it is not a bug - please can you explain

[Fedik]

It is PHP side (PHP GD), not Joomla.
All we can do is try to set "quality" https://www.php.net/manual/en/function.imagepng.php different from default.

How can it be expected to reduce the dimensions of a png and yet the filesize increases by 300%

Depend from amount of detail the image have, it can happen for PNG in any application, not only PHP

[brianteeman]

As the purpose of creating the thumbnail is to crerate a fast loading version of the image and this thumbnail will only be displayed in the media manager why not always set the compression to the maximum.

Otherwise any png that has been optimised before uploading to joomla will generate a larger file when resized

[brianteeman]

The code exists already to select the image quality. Its just not used at all so the compression defaults to 0 :(

[Fedik]

It a bit tricky, PNG have a range -1 ... 9, JPG -1 .. 100.
Need an extra logic, extra code, but should be possible.
Someone can try.

I just can't say how much it will really help. For cases when User upload "optimised PNG", the thumbnail still may be bigger after PHP processing.

As the purpose of creating the thumbnail is to crerate a fast loading version of the image

Well, it is more for really large (resolution) images , for images with small resolutions it probably irrelevant

[brianteeman]

I did a quick manual try with PNG set to 9 and the difference was amazing.

Our code supports different settings for jpg and png compression/quality it's just not being used for the thumbs

[dgrammatiko]

@brianteeman although the Image class supports different compression ratios the functionality for the thumbnails doesn't expose it:

joomla-cms/plugins/filesystem/local/src/Adapter/LocalAdapter.php

Line 955 in 45adb61

$image->createThumbnails([$this->thumbnailSize[0] . 'x' . $this->thumbnailSize[1]], $image::SCALE_INSIDE, dirname($thumbnailPath), true);

joomla-cms/libraries/src/Image/Image.php

Line 319 in 45adb61

public function createThumbnails($thumbSizes, $creationMethod = self::SCALE_INSIDE, $thumbsFolder = null, $useOriginalName = false)

I did the implementation for the thumbnails so I guess this is my fault, if you need to blame somebody

[brianteeman]

not interested in blame - just interested in making the thumbs functionality work as intended. I am certain you didnt intent to make the thumbnails bigger than the original ;)

[dgrammatiko]

If you still have the test site available could you try adding:

$image->setThumbnailGenerate(false);

after: https://github.com/joomla/joomla-cms/blob/45adb61f8306b945f43b4326305fafe87c154aa2/plugins/filesystem/local/src/Adapter/LocalAdapter.php#L952C9-L952C35

Should do the trick

[brianteeman]

surely that just disabled the creation of thumbnails ??

[dgrammatiko]

surely that just disabled the creation of thumbnails ??

The docs say that this controls the quality:

joomla-cms/libraries/src/Image/Image.php

Lines 1124 to 1133 in 45adb61

	/**
	* Method for set option of generate thumbnail method
	*
	* @param boolean $quality True for best quality. False for best speed.
	*
	* @return void
	*
	* @since 3.7.0
	*/
	public function setThumbnailGenerate($quality = true)

[brianteeman]

my bad - i will test that soon

[brianteeman]

all that does is to create reall bad quality thumbnails that are the same filesize as the good ones

filename	original filesize kb	cache filesize kb	cache filesize after
image1.png	44.05	105.85	1-5.85
image2.png	452.83	75.3	75.3
image3.png	30.47	93.39	93.39
image4.jpg	250.94	27.79	31.34
image5.jpg	114.55	26	30.48
image6.jpg	260.38	34.84	42.02

[dgrammatiko]

@brianteeman check #43282

[alikon]

please test #43282