png vs. jpeg

So one of the best memories of taking 505 in CCT was FINALLY understanding how jpeg works. It actually felt like opening a black box and unlocked the secret of a magician.

With one question answered I have a dozen more. I started to wonder how other image formats work, especially why PNG can create transparency in image and jpeg cannot. Hence I did some research and found out why. Instead of using difficult jargons, I will try to explain the difference between PNG and jpeg through my crude words.

So jpeg is made with different segments, each segment has a marker in the beginning telling what color a pixel is and how many pixels of the same color exist sequentially. These segments are structured using binary codes. With the correct way of decoding, one will be able to view the image on any device that supports jpeg. Because jpeg’s syntactic structure, it will be difficult to represent absent of color and how absent some colors should be, therefore it is difficult to represent transparency.

Though PNG is also coded in a binary manner using only 1 and 0. The structure of PNG allow it to do more than just tell what color a pixel is and how to arrange the order. Each segment in PNG has a special task such as organize the frame, adjust the color, and how much space is between one color and the other. Therefore, PNG can have transparent background and jpeg cannot.

What is so cool about these two format is that one image can totally different syntactic structure in different formats. This also an evidence to Pierce’ claim that signs as vehicles do not possess meanings. Like these images, they are only meaningful to us when they are properly decoded, or decompressed in this case. Taking a photo and make that into a jpeg means to translate that into a string of binary codes. These codes become vehicle of what the photo represent. These codes are then decoded on our computer and then we can interact with the image and create meanings out of it.

It is remarkable how much we can achieve through digital representation, and how much we can make the convey of meaning more efficient and accurate. Here is an example. The video shows the compression speech difference between PNG and FLIF, a newly developed image format.

Though the meaning we can get from these images are the same, the speech of FILF makes the delivery of meaning so much faster and that is meaningful in a different manner.