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Tag: Image::Magick

The way to check if JPEG file is progressive or not

There are two type of JPEG picture file.

  • Regular JPEG, or baseline JPEG.
  • Progressive JPEG, or Interlace JPEG.

It is very common, same quality picture, progressive jpeg is smaller than regular jpeg. And also progressive jpeg can show the content when the picture is download. This kind of show is to shown the whole picture with low quality then clear and clear, until whole picture is downloaded.

So, of course, if it is possible, we alwasy want to use progressive JPEG. Some old files need to be convert to progressive. But, before that, we have to identify which JPEG file is regular, which one is progressive already.

There is no simply way to check if a JPEG file is progressive on Windows.

I have CentOS server. It has ImageMagick.

I would like to introduce how to check if JPEG is progressive with ImageMagick.

identify -verbose file.jpg | grep Interlace

If the result is Interlace:JPEG it is progressive. If it say Interlace:None, then it is a baseline.



Why thumbnail png file is bigger after original png

I use png format picture file sometimes. It is OK when I upload the file into MovableType platform. I choose make thumbnail to 400px width from about 700px.
Perl ImageMagick engine will create thumbnail file. The blog software will generate html code and put into editor body.
Everything looks find. But the file size of thumbnail png is bigger than original png file.
Original png file: 700X505 49KB
Thumbnail png file: 400X288 78KB
Why is it bigger?

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Install the Perl Image::Magick on Centos

I have an VPS at I pick up Centos 5.5 installation. To make MovableType work on it, I have to install Perl module Image::Magick. The image thumbnail feature will be disabled if no Image::Magick installed.

Every time I do it, I always have the problem to install it. Now I recorded here for reference.

Here is the official guide for installation of ImageMagick. I follow the instruction, but it is still not working.

So I use the way suggested on above link.
The handy notes provided by John Walker. The rest of this post are based on this notes mostly.

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