c# 圖文添加文字斜水印 優化

之前一篇給圖片加水印的功能，加出來水印的圖片位置有一點問題，並且如果圖片分辨率有變動的話，水印會有層次不齊的問題。

目前只能優化到增加一條居中顯示的斜水印，在不同分辨率不同大小的圖片中，都能保證文字水印的字體大小從左下至右上能撐滿整張圖片。

 

思路是：先生成一張文字水印圖片的PNG圖片。

 

在你需要添加水印的圖片上，把之前加的水印圖片貼上去就可以了。

 

核心代碼：

    //新建原始普通大小的bmp
    Bitmap bmCanvas = new Bitmap(imgSrc.Width, imgSrc.Height, PixelFormat.Format24bppRgb);
    Graphics gCanvas = Graphics.FromImage(bmCanvas);
    gCanvas.Clear(Color.White);
    gCanvas.SmoothingMode = SmoothingMode.HighQuality;
    gCanvas.InterpolationMode = InterpolationMode.High;
    //將原始圖片加載入畫布
    gCanvas.DrawImage(imgSrc, 0, 0, imgSrc.Width, imgSrc.Height);
    //計算圖片對角線長度
    double diagonal = Math.Sqrt(Math.Pow(width, 2) + Math.Pow(height, 2));
    
    //計算對角線傾角
    double angle = Math.Asin(height / Math.Sqrt(Math.Pow(width, 2) + Math.Pow(height, 2))) / Math.PI * 180;
    
    // 確定水印文字的字體大小
    int[] sizes = new int[]
    {
        280, 276, 272, 268, 264, 260, 256, 252, 248, 244, 240, 236, 232, 228, 224, 220, 216, 212, 208,
        204, 200, 196, 192, 188, 184, 180, 176, 172, 168, 164, 160, 156, 152, 148, 144, 140, 136, 132,
        128, 124, 120, 116, 112, 108, 104, 100, 96, 92, 88, 84, 80, 76, 72, 68, 64, 60, 56, 52, 48, 44,
        40, 36, 32, 28, 24, 20, 16, 12, 8, 4
    };
    Font crFont = null;
    SizeF crSize = new SizeF();
    
    for (int i = 0; i < sizes.Length; i++)
    {
        crFont = new Font("微軟雅黑", sizes[i], FontStyle.Bold);
        crSize = gCanvas.MeasureString(watermarkText, crFont);
        if ((int)crSize.Width < (int)diagonal * 0.9)
        {
            break;
        }
    }
    // 生成水印圖片（將文字寫到圖片中）
    //Bitmap bmWaterMark = new Bitmap((int)crSize.Width + 3, (int)crSize.Height + 3, PixelFormat.Format32bppArgb);
    Bitmap bmWaterMark = new Bitmap(width, height, PixelFormat.Format32bppArgb);
    Graphics gWaterMark = Graphics.FromImage(bmWaterMark);
    
    gWaterMark.TranslateTransform(width / 2, height / 2);
    gWaterMark.RotateTransform(-(int)angle);
    gWaterMark.TranslateTransform(-crSize.Width / 2, -crSize.Height / 2);
    
    PointF pt = new PointF(0, 0);
    // 畫陰影文字
    Brush transparentBrush0 = new SolidBrush(Color.FromArgb(255, Color.Black));
    Brush transparentBrush1 = new SolidBrush(Color.FromArgb(255, Color.Black));
    gWaterMark.DrawString(watermarkText, crFont, transparentBrush0, pt.X, pt.Y + 1);
    gWaterMark.DrawString(watermarkText, crFont, transparentBrush0, pt.X + 1, pt.Y);
    gWaterMark.DrawString(watermarkText, crFont, transparentBrush1, pt.X + 1, pt.Y + 1);
    gWaterMark.DrawString(watermarkText, crFont, transparentBrush1, pt.X, pt.Y + 2);
    gWaterMark.DrawString(watermarkText, crFont, transparentBrush1, pt.X + 2, pt.Y);
    transparentBrush0.Dispose();
    transparentBrush1.Dispose();
    
    // 畫文字
    gWaterMark.SmoothingMode = SmoothingMode.HighQuality;
    //Brush SolidBrush3 = new SolidBrush(Color.White);
    Brush solidBrush3 = new SolidBrush(Color.FromArgb(255, Color.White));
    gWaterMark.DrawString(watermarkText, crFont, solidBrush3, pt.X, pt.Y, StringFormat.GenericDefault);
    solidBrush3.Dispose();
    
    // 保存剛才的操作
    gWaterMark.Save();
    gWaterMark.Dispose();
    bmWaterMark.Save(_wmImgSavePath, ImageFormat.Jpeg);
    
    //// 將水印圖片加到原圖中
    //AddWatermarkImage(gCanvas, new Bitmap(bmWaterMark), "WM_TOP_LEFT", width, height);
    
    using (var imageAttr = new ImageAttributes())
    {
        ColorMap colorMap = new ColorMap();
        colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
        colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
        ColorMap[] remapTable = { colorMap };
        imageAttr.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
        float[][] colorMatrixElements =
        {
            new float[] {1.0f, 0.0f, 0.0f, 0.0f, 0.0f},
            new float[] {0.0f, 1.0f, 0.0f, 0.0f, 0.0f},
            new float[] {0.0f, 0.0f, 1.0f, 0.0f, 0.0f},
            new float[] {0.0f, 0.0f, 0.0f, 0.3f, 0.0f},
            new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}
        };
        ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);
        imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
        gCanvas.DrawImage(bmWaterMark, new Rectangle(10, 10, bmWaterMark.Width, bmWaterMark.Height), 0, 0,
            bmWaterMark.Width, bmWaterMark.Height, GraphicsUnit.Pixel, imageAttr);
        gCanvas.Dispose();
    }
    bmWaterMark.Dispose();

 

代碼已上傳至GitHub，地址：https://github.com/hano7758/WaterMark