Function put_text

rustcv/src/imgproc/drawing.rs:123–163

在图像上绘制文字

(mat: &mut Mat, text: &str, org: Point, font_scale: f32, color: Scalar)

/// 在图像上绘制文字
pub fn put_text(mat: &mut Mat, text: &str, org: Point, font_scale: f32, color: Scalar) {
    let font = get_font();
    let scale = Scale::uniform(font_scale * 20.0); // 调整倍率以匹配 OpenCV 手感
    let start = point(org.x as f32, org.y as f32);
    let glyphs: Vec<PositionedGlyph> = font.layout(text, scale, start).collect();

    let step = mat.step;
    let rows = mat.rows;
    let cols = mat.cols;
    let channels = 3;

    for glyph in glyphs {
        if let Some(bounding_box) = glyph.pixel_bounding_box() {
            // 栅格化每个字符
            glyph.draw(|x, y, v| {
                // v 是覆盖率 (0.0 - 1.0)，用于抗锯齿混合
                let px = x as i32 + bounding_box.min.x;
                let py = y as i32 + bounding_box.min.y;

                if px >= 0 && px < cols && py >= 0 && py < rows {
                    let idx = (py as usize) * step + (px as usize) * channels;

                    // 简单的 Alpha Blending
                    // Current Pixel
                    let b_old = mat.data[idx] as f32;
                    let g_old = mat.data[idx + 1] as f32;
                    let r_old = mat.data[idx + 2] as f32;

                    let alpha = v;
                    let b_new = (color.v0 as f32 * alpha) + (b_old * (1.0 - alpha));
                    let g_new = (color.v1 as f32 * alpha) + (g_old * (1.0 - alpha));
                    let r_new = (color.v2 as f32 * alpha) + (r_old * (1.0 - alpha));

                    mat.data[idx] = b_new as u8;
                    mat.data[idx + 1] = g_new as u8;
                    mat.data[idx + 2] = r_new as u8;
                }
            });
        }
    }
}