Golang : Fix image: unknown format error

Problem :

You want to find out the dimension of an image file with image.DecodeConfig() function - to get the color model, width and height. However, while doing so, you get this strange error message :

image : unknown format error

How to fix this problem?

Solutions :

1) The image.DecodeConfig() function is either reading an empty file or pointer to empty file. Before calling image.DecodeConfig(inputFile), perform sanity check on the input file. Is the size zero? Is the file is actually a directory? A common mistake is that the inputFile parameter only contains the filename, but not the full path. i.e missing the directory.

You may need to use the path/filepath.Abs() function. See https://www.socketloop.com/references/golang-path-filepath-abs-function-example

2) Also remember, to import image/jpeg, image/png and image/gif and initialize them at the init() function. See https://www.socketloop.com/references/golang-image-registerformat-function-example

Reference :

https://www.socketloop.com/tutorials/golang-get-dimension-width-and-height-of-image-file