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import gleam/int
pub type ImageInformation {
ImageInformation(width: Int, height: Int, extension: String)
}
pub fn get_image_information(image) {
case image {
<<0x89, "PNG\r\n":utf8, 0x1A, 0x0A, _:bits>> -> parse_png_chunks(image, 8)
<<
"GIF":utf8,
_:16,
_:unsigned,
width_0:8,
width_1:8,
height_0:8,
height_1:8,
_rest:bits,
>> ->
Ok(ImageInformation(
int.bitwise_or(width_0, int.bitwise_shift_left(width_1, 8)),
int.bitwise_or(height_0, int.bitwise_shift_left(height_1, 8)),
"gif",
))
_ -> Error("Unsupported image format")
}
}
fn parse_png_chunks(image, offset) {
let offset_bits = offset * 8
case image {
<<
_:size(offset_bits),
_length:32,
"IHDR":utf8,
width:32,
height:32,
_:bits,
>> -> Ok(ImageInformation(width, height, "png"))
<<_:size(offset), length:32, _:4, _:bits>> ->
parse_png_chunks(image, offset + length + 12)
_ -> Error("Invalid PNG chunk")
}
}
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