數據URI格式是否有重要的部分？

Question

數據URI的紅點：

<img src='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==' height='32' width='32' alt='Image'>

如果任何這裏的部分？例如，該類型的前20個字符是否保留，後面的2個是否爲不透明等？如果任何人都可以指引我到正確的地方，我無法找到互聯網上的任何東西！

確定爲PNG有相似之處的字符串： iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAh7sky7OeYKB8+tP6XGdtx//a/E2m63tavY/hRM=qW+lVt1OD8sxrieE5j7ebvK3eiz+1==eV=Crr4=

和

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

第20-30類似輕微variancies： iVBORw0KGgoAAAANSUhEUgAAAEAAAABACAAAAACPA

但我無法確定任何格式/模式。使用=或/我會看RFC，但是這仍然是開放的......

Answer 1

data:   Required, data-URI protocol 
image/png  Required, MIME-type 
;charset=UTF8 Optional, character encoding 
;base64  Optional 
,    Required 
...   Optional: 
       Note: When ;base64 is set, a valid base64 string has to be given 

參見：

• 堆棧溢出的答案：What are special characters in data-URIs?
• 百科：Data URI scheme
• 維基百科：Base64