Why ImportByteArray when generate image from bytes

Question

I was trying to generate an image from a list of bytes so I only had to Import an Image once as I want to store a Base64Encoded string in a database using the Imported bytes.

I found one solution but not sure why ImportByteArray is needed when generating an Image from bytes?

image = Import[
  "http://www.wolfram.com/common/framework/img/spikey.en.png", "Image"]

imageBytes = 
 Import["http://www.wolfram.com/common/framework/img/spikey.en.png", 
  "Byte"]

imageBinary = 
 Import["http://www.wolfram.com/common/framework/img/spikey.en.png", 
  "Binary"]

imageBytes === imageBinary 
(*true*)

imageBytes === Normal[BinarySerialize[image]]
(*False*)

To Generate Image from bytes, one solution is:

decodedImage = Image[ImportByteArray[ByteArray[imageBytes]], "Byte"]

decodedImage === image
(*True*)

Why do you need the ImportByteArray? You should be able to:

imageData = Image[imageBytes, "Byte"]
(*ERROR Image::imgarray*)

This also does not work:

imageData = Image[ByteArray[imageBytes], "Byte"]

Answer 1

There are a couple of issues here. First, the full text of Image::imgarray sheds light on one issue:

Image::imgarray: The specified argument ByteArray[2.3 kB] should be an array of rank 2 or 3 with machine-sized numbers.

Specifically, Image does not know how to turn a vector of numbers into a matrix. Second, and more interestingly, Image does not work with image formats, but the equivalent, underlying data. Simply, imageBytes is still in its original format

In[14]:= ByteArrayFormat@ByteArray[imageBytes]
Out[14]= "PNG"

So, ImportByteArray is needed to convert this from formatted data to raw data.