Invalid base64 data on input byte 4 when using base64.StdEncoding.DecodeString (str)
I am getting: error: illegal base64 data at input byte 4
When passing Base64Image to base64.StdEncoding.DecodeString(str)
:
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAYA...
Let me know if you want the full base64, I just pasted the first part in, so it looks like the problem is 4 bytes?
data, errBase := base64.StdEncoding.DecodeString(Base64Image)
if errBase != nil {
fmt.Println("error:", errBase)
return false
}
You know why?
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Not all of your input string you are trying to decode is Base64 encoded.
You have a data URI scheme that provides a way to include data in a string in web pages as if it were external resources.
It has the format:
data:[<MIME-type>][;charset=<encoding>][;base64],<data>
Where in your case image/png
is the MIME type, there is no optional encoding, and ";base64"
is a constant string indicating what <data>
is encoded using Base64 encoding.
To get the data (i.e. Base64 encoding), disable the prefix before the comma (including the comma):
input := "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAYA"
b64data := input[strings.IndexByte(input, ',')+1:]
fmt.Println(b64data)
Output:
iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAYA
From which you can now decode:
data, err := base64.StdEncoding.DecodeString(b64data)
if err != nil {
fmt.Println("error:", err)
}
fmt.Println(data)
Output:
[137 80 78 71 13 10 26 10 0 0 0 13 73 72 68 82 0 0 0 100 0 0 0 100 8 6 0]
Try it on the Go Playground .
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This is because your string is not in base64 until the data is comma: image / png; base64, iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAYA ...
import "strings" and use split to get the half after the decimal point and then call decodestring with that.
import "strings"
data, errBase := base64.StdEncoding.DecodeString(strings.Split(Base64Image, "base64,")[1]))
if errBase != nil {
fmt.Println("error:", errBase)
return false
}
EDIT: Made a split token base64,
because it's more specific to your input.
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