Speed up image stuff (#223)

* Get the dimensions without reading the full image into memory

This is faster than fully loading the image and then getting its dimensions.

* Introduce a way to insert images as a byte buffer

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "umya-spreadsheet"
-version = "2.0.2"
+version = "2.0.3"
 authors = ["MathNya <[email protected]>"]
 repository = "https://github.com/MathNya/umya-spreadsheet"
 keywords = ["excel", "spreadsheet", "xlsx", "reader", "writer"]
@@ -24,7 +24,7 @@ getrandom = { version = "0.2.14" }
 hashbrown = "0.14.3"
 hmac = "0.12.1"
 html_parser = "0.7.0"
-image = "0.25.0"
+image = { version = "0.25.0", optional = true }
 lazy_static = "1.4.0"
 md-5 = "0.10.6"
 regex = "1.10.2"
@@ -38,3 +38,4 @@ doctest = false
 
 [features]
 js = ["getrandom/js"]
+default = ["image"]

src/structs/image.rs

@@ -1,10 +1,10 @@
 use base64::{engine::general_purpose::STANDARD, Engine as _};
-use image::GenericImageView;
 use quick_xml::Writer;
 use std::fs;
 use std::fs::File;
 use std::io::Cursor;
 use std::io::Read;
+use std::io::BufReader;
 use structs::drawing::spreadsheet::MarkerType;
 use structs::drawing::spreadsheet::OneCellAnchor;
 use structs::drawing::spreadsheet::Picture;
@@ -97,18 +97,21 @@ impl Image {
         self
     }
 
+    #[cfg(feature = "image")]
     pub fn new_image(&mut self, path: &str, marker: MarkerType) {
-        let path_str = path;
-        let path_obj = std::path::Path::new(path_str);
-        let image_name = path_obj.file_name().unwrap().to_str().unwrap();
+        let path = std::path::Path::new(path);
 
-        let img = image::open(path_obj).unwrap();
-        let (width, height) = img.dimensions();
-
-        let mut file = File::open(path_str).unwrap();
+        let (width, height) = image::image_dimensions(path).unwrap();
+        let image_name = path.file_name().unwrap().to_str().unwrap();
         let mut buf = Vec::new();
-        file.read_to_end(&mut buf).unwrap();
 
+        let file = File::open(path).unwrap();
+        BufReader::new(file).read_to_end(&mut buf).unwrap();
+
+        self.new_image_with_dimensions(height, width, image_name, buf, marker)
+    }
+
+    pub fn new_image_with_dimensions<B: Into<Vec<u8>>>(&mut self, height: u32, width: u32, image_name: &str, bytes: B, marker: MarkerType) {
         let mut picture = Picture::default();
         // filename and filedata.
         picture
@@ -117,7 +120,7 @@ impl Image {
             .set_cstate("print")
             .get_image_mut()
             .set_image_name(image_name)
-            .set_image_data(buf);
+            .set_image_data(bytes.into());
 
         // name
         picture