QRGen/core/src/render/image.rs

//! QR 码图像渲染（支持 PNG/BMP/JPEG/WebP）
//!
//! 使用 `image` crate 将 QR 模块矩阵渲染为像素缓冲区，可选叠加 Logo。

use crate::qr::QrCode;
use image::{imageops, ImageBuffer, Rgba, RgbaImage};

/// 输出图像格式
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum OutputFormat {
    Png,
    Bmp,
    Jpeg,
    WebP,
}

impl OutputFormat {
    /// 转为 `image` crate 的格式枚举
    fn to_image_format(self) -> image::ImageFormat {
        match self {
            Self::Png => image::ImageFormat::Png,
            Self::Bmp => image::ImageFormat::Bmp,
            Self::Jpeg => image::ImageFormat::Jpeg,
            Self::WebP => image::ImageFormat::WebP,
        }
    }

    /// 文件扩展名（不含点）
    pub fn extension(self) -> &'static str {
        match self {
            Self::Png => "png",
            Self::Bmp => "bmp",
            Self::Jpeg => "jpeg",
            Self::WebP => "webp",
        }
    }

    /// MIME 类型
    pub fn mime(self) -> &'static str {
        match self {
            Self::Png => "image/png",
            Self::Bmp => "image/bmp",
            Self::Jpeg => "image/jpeg",
            Self::WebP => "image/webp",
        }
    }

    /// 从扩展名解析
    pub fn from_ext(ext: &str) -> Option<Self> {
        match ext.to_lowercase().as_str() {
            "png" => Some(Self::Png),
            "bmp" => Some(Self::Bmp),
            "jpeg" | "jpg" => Some(Self::Jpeg),
            "webp" => Some(Self::WebP),
            _ => None,
        }
    }
}

fn fill_module(
    img: &mut RgbaImage,
    x: u32,
    y: u32,
    module_size: u32,
    is_dark: bool,
    fg: &[u8; 3],
    bg: &[u8; 3],
) {
    let color = if is_dark {
        Rgba([fg[0], fg[1], fg[2], 255])
    } else {
        Rgba([bg[0], bg[1], bg[2], 255])
    };
    let x0 = x * module_size;
    let y0 = y * module_size;
    for dy in 0..module_size {
        for dx in 0..module_size {
            img.put_pixel(x0 + dx, y0 + dy, color);
        }
    }
}

fn overlay_logo(img: &mut RgbaImage, logo_bytes: &[u8], logo_size_pct: f32) -> Result<(), String> {
    let logo = image::load_from_memory(logo_bytes).map_err(|e| format!("Logo 加载失败: {e}"))?;
    let logo = logo.to_rgba8();
    let img_w = img.width();
    let img_h = img.height();
    let logo_size = (img_w.min(img_h) as f32 * logo_size_pct) as u32;
    if logo_size < 4 {
        return Ok(());
    }
    let resized = imageops::resize(&logo, logo_size, logo_size, imageops::FilterType::Lanczos3);
    let x = (img_w - logo_size) / 2;
    let y = (img_h - logo_size) / 2;
    imageops::overlay(img, &resized, x as i64, y as i64);
    Ok(())
}

/// 渲染 QR 码到图像字节（支持 PNG/BMP/JPEG/WebP）
pub fn render_image(
    qr: &QrCode,
    module_size: u8,
    format: OutputFormat,
    logo: Option<&[u8]>,
) -> Result<Vec<u8>, image::ImageError> {
    let matrix_size = qr.size() as u32;
    let margin = qr.margin as u32;
    let total_size = matrix_size + 2 * margin;
    let img_size = total_size * module_size as u32;

    let mut img = ImageBuffer::new(img_size, img_size);

    for y in 0..total_size {
        for x in 0..total_size {
            let is_dark = if x >= margin
                && x < margin + matrix_size
                && y >= margin
                && y < margin + matrix_size
            {
                let mx = (x - margin) as usize;
                let my = (y - margin) as usize;
                qr.modules()[my][mx]
            } else {
                false
            };
            fill_module(
                &mut img,
                x,
                y,
                module_size as u32,
                is_dark,
                &qr.fg_color,
                &qr.bg_color,
            );
        }
    }

    if let Some(logo_data) = logo {
        let _ = overlay_logo(&mut img, logo_data, 0.25);
    }

    let mut buf = Vec::new();
    img.write_to(
        &mut std::io::Cursor::new(&mut buf),
        format.to_image_format(),
    )?;
    Ok(buf)
}