Reduce default image size to 220x70 and output JPEG to improve perfor…

…mance (181.238 i/s -> 526.350 i/s).

README.md

@@ -169,8 +169,7 @@ end
 
 ```
 Warming up --------------------------------------
-      Generate image    18.000  i/100ms
+      Generate image    51.000  i/100ms
 Calculating -------------------------------------
-      Generate image (2.6.x  C Version)   181.238  (± 2.8%) i/s -    918.000  in   5.069689s
-      Generate image (3.x Rust version)   165.047  (±15.8%) i/s -    792.000  in   5.003023s
+      Generate image    526.350  (± 2.5%) i/s -      2.652k in   5.041681s
 ```

app/controllers/ru_captcha/captcha_controller.rb

@@ -7,7 +7,7 @@ def index
       headers["Pragma"] = "no-cache"
       data = generate_rucaptcha
 
-      opts = { disposition: "inline", type: "image/png" }
+      opts = { disposition: "inline", type: "image/jpeg" }
       send_data data, opts
     end
   end

ext/rucaptcha/src/captcha.rs

@@ -1,6 +1,6 @@
 use image::{ImageBuffer, Rgb};
 use imageproc::drawing::{draw_cubic_bezier_curve_mut, draw_text_mut};
-use imageproc::noise::{gaussian_noise_mut, salt_and_pepper_noise_mut};
+use imageproc::noise::gaussian_noise_mut;
 use rand::{thread_rng, Rng};
 use rusttype::{Font, Scale};
 use std::io::Cursor;
@@ -195,8 +195,8 @@ impl CaptchaBuilder {
     pub fn new() -> Self {
         CaptchaBuilder {
             length: 4,
-            width: 300,
-            height: 100,
+            width: 220,
+            height: 70,
             complexity: 5,
         }
     }
@@ -247,15 +247,9 @@ impl CaptchaBuilder {
             ((5 * self.complexity) - 5) as u64,
         );
 
-        salt_and_pepper_noise_mut(
-            &mut image,
-            ((0.001 * self.complexity as f64) - 0.001) as f64,
-            (0.8 * self.complexity as f64) as u64,
-        );
-
         let mut bytes: Vec<u8> = Vec::new();
         image
-            .write_to(&mut Cursor::new(&mut bytes), image::ImageFormat::Png)
+            .write_to(&mut Cursor::new(&mut bytes), image::ImageFormat::Jpeg)
             .unwrap();
 
         Captcha { text, image: bytes }