qrcode-rs 0.3.0

QR code encoder in Rust，Generate QR Code matrices and images in RAW, PNG and SVG formats.
Documentation 
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//! HTML rendering support.
//!
//! Generates HTML `<table>` or CSS Grid output for embedding QR codes in web pages.
//!
//! # Example
//!
//! ```
//! use qrcode_rs::QrCode;
//! use qrcode_rs::render::html::Color;
//!
//! let code = QrCode::new(b"Hello").unwrap();
//! let html = code.render::<Color>().build();
//! println!("{}", html);
//! ```

#![cfg(feature = "html")]

use std::marker::PhantomData;

use crate::cast::As;
use crate::render::{Canvas as RenderCanvas, Pixel};
use crate::types::Color as ModuleColor;

/// Rendering mode for HTML output.
#[derive(Copy, Clone, Default, PartialEq, Eq)]
pub enum Mode {
    /// Generate HTML `<table>` (default).
    #[default]
    Table,
    /// Generate `<div>` with CSS Grid layout.
    Grid,
}

/// An HTML color.
#[derive(Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Color<'a>(pub &'a str);

impl<'a> Pixel for Color<'a> {
    type Image = String;
    type Canvas = Canvas<'a>;

    fn default_unit_size() -> (u32, u32) {
        (1, 1)
    }

    fn default_color(color: ModuleColor) -> Self {
        Color(color.select("#000", "#fff"))
    }
}

#[doc(hidden)]
pub struct Canvas<'a> {
    dark_pixels: Vec<bool>,
    width: u32,
    height: u32,
    dark_color: &'a str,
    light_color: &'a str,
    mode: Mode,
    marker: PhantomData<Color<'a>>,
}

impl<'a> Canvas<'a> {
    /// Sets the HTML rendering mode (Table or Grid).
    pub fn set_mode(&mut self, mode: Mode) {
        self.mode = mode;
    }
}

impl<'a> RenderCanvas for Canvas<'a> {
    type Pixel = Color<'a>;
    type Image = String;

    fn new(width: u32, height: u32, dark_pixel: Color<'a>, light_pixel: Color<'a>) -> Self {
        Canvas {
            dark_pixels: vec![false; (width * height).as_usize()],
            width,
            height,
            dark_color: dark_pixel.0,
            light_color: light_pixel.0,
            mode: Mode::default(),
            marker: PhantomData,
        }
    }

    fn draw_dark_pixel(&mut self, x: u32, y: u32) {
        let idx = (y * self.width + x).as_usize();
        if idx < self.dark_pixels.len() {
            self.dark_pixels[idx] = true;
        }
    }

    fn into_image(self) -> String {
        match self.mode {
            Mode::Table => self.into_table(),
            Mode::Grid => self.into_grid(),
        }
    }
}

impl<'a> Canvas<'a> {
    fn into_table(self) -> String {
        let cap = 512 + (self.width * self.height * 20) as usize;
        let mut html = String::with_capacity(cap);
        html.push_str(r#"<!DOCTYPE html><html><head><meta charset="UTF-8"></head><body><table style="border-collapse:collapse;line-height:0">"#);

        for y in 0..self.height {
            html.push_str("<tr>");
            for x in 0..self.width {
                let idx = (y * self.width + x).as_usize();
                let color = if self.dark_pixels[idx] { self.dark_color } else { self.light_color };
                html.push_str(r#"<td style="width:1px;height:1px;background:"#);
                html.push_str(color);
                html.push_str(r#""></td>"#);
            }
            html.push_str("</tr>");
        }

        html.push_str("</table></body></html>");
        html
    }

    fn into_grid(self) -> String {
        let cap = 512 + (self.width * self.height * 10) as usize;
        let mut html = String::with_capacity(cap);
        html.push_str(r#"<!DOCTYPE html><html><head><meta charset="UTF-8"></head><body><div style="display:grid;grid-template-columns:repeat("#);
        html.push_str(&self.width.to_string());
        html.push_str(r#",1px);line-height:0">"#);

        for y in 0..self.height {
            for x in 0..self.width {
                let idx = (y * self.width + x).as_usize();
                let color = if self.dark_pixels[idx] { self.dark_color } else { self.light_color };
                html.push_str(r#"<div style="width:1px;height:1px;background:"#);
                html.push_str(color);
                html.push_str(r#""></div>"#);
            }
        }

        html.push_str("</div></body></html>");
        html
    }
}

#[cfg(test)]
mod tests {
    use crate::QrCode;
    use crate::render::html::Color;

    #[test]
    fn test_html_table_render() {
        let code = QrCode::new(b"Hello").unwrap();
        let html = code.render::<Color>().build();
        assert!(html.contains("<!DOCTYPE html>"));
        assert!(html.contains("<table"));
        assert!(html.contains("</table>"));
        assert!(html.contains("#000"));
        assert!(html.contains("#fff"));
    }

    #[test]
    fn test_html_custom_colors() {
        let code = QrCode::new(b"Hi").unwrap();
        let html = code.render::<Color>().dark_color(Color("#333")).light_color(Color("#eee")).build();
        assert!(html.contains("#333"));
        assert!(html.contains("#eee"));
    }
}