c# 图片自动去黑边思路

1、如果某一行(列)的所有像素点的颜色相差不大，则判断为黑边/白边

2、按照1方法依次去除上、下、左、右黑边/白边

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

public Bitmap CropBitmap(Bitmap originalBitmap, int top, int bottom, int left, int right)
        {
            // 计算新的图像大小
            int newWidth = originalBitmap.Width - left - right;
            int newHeight = originalBitmap.Height - top - bottom;
 
            // 创建新的 Bitmap 对象
            Bitmap croppedBitmap = new Bitmap(newWidth, newHeight);
 
            // 创建一个 Graphics 对象，用于绘制新的图像
            Graphics g = Graphics.FromImage(croppedBitmap);
 
            // 绘制原始图像的一部分到新的图像中
            g.DrawImage(originalBitmap, new Rectangle(0, 0, newWidth, newHeight), new Rectangle(left, top, newWidth, newHeight), GraphicsUnit.Pixel);
 
            // 释放 Graphics 对象
            g.Dispose();
 
            // 返回裁剪后的图像
            return croppedBitmap;
        }
 
        //去除上黑边
        private Bitmap RemoveUpBlackEdge(Bitmap image)
        {
            int height = image.Height;
            int width = image.Width;
 
            Color firstPixel = image.GetPixel(0, 0); // 获取左上角第一个像素的颜色
 
            int diffLine = 0; // 顶部黑边行数
 
            for (int y = 0; y < height; y++) // 从第一行开始比较
            {
                bool darkLine = true;
                for (int x = 0; x < width; x++)
                {
                    Color pixel = image.GetPixel(x, y);
 
                    int deltaR = Math.Abs(pixel.R - firstPixel.R);
                    int deltaG = Math.Abs(pixel.G - firstPixel.G);
                    int deltaB = Math.Abs(pixel.B - firstPixel.B);
                    int deltaTotal = deltaR + deltaG + deltaB;
 
                    if (deltaTotal > 500 || deltaTotal < -500)
                    {
                        darkLine = false;
                        break;
                    }
                     
                }
                diffLine++;
                if (!darkLine) // 如果这一行和第一行不同，记录下这一行的行数
                {
                    break;
                }
            }
            return CropBitmap(image, diffLine, 0, 0, 0);
 
        }
 
        //去除下黑边
        private Bitmap RemoveDownBlackEdge(Bitmap image)
        {
            int height = image.Height;
            int width = image.Width;
 
            Color firstPixel = image.GetPixel(0, height-1); // 获取左下角第一个像素的颜色
 
            int diffLine = 0; // 底部黑边行数
 
            for (int y = height - 1; y > 1; y--) // 从最后一行开始比较
            {
                bool darkLine = true;
                for (int x = 0; x < width; x++)
                {
                    Color pixel = image.GetPixel(x, y);
 
                    int deltaR = Math.Abs(pixel.R - firstPixel.R);
                    int deltaG = Math.Abs(pixel.G - firstPixel.G);
                    int deltaB = Math.Abs(pixel.B - firstPixel.B);
                    int deltaTotal = deltaR + deltaG + deltaB;
 
                    if (deltaTotal > 500 || deltaTotal < -500)
                    {
                        darkLine = false;
                        break;
                    }
                }
                diffLine++;
                if (!darkLine) // 如果这一行和第一行不同，记录下这一行的行数
                {
                    break;
                }
            }
 
            if (diffLine == 0) // 如果所有行都相同
            {
                return image;
            }
            else // 如果有不同的行
            {
                return CropBitmap(image, 0, diffLine, 0, 0);
            }
        }
 
        private Bitmap RemoveLeftBlackEdge(Bitmap image)
        {
            int height = image.Height;
            int width = image.Width;
 
            Color firstPixel = image.GetPixel(0, 0); // 获取第一个像素的颜色
 
            int diffLine = 0; // 顶部黑边行数
 
            for (int x = 0; x < width; x++) // 从第一行开始比较
            {
                bool darkLine = true;
                for (int y = 0; y < height; y++)
                {
                    Color pixel = image.GetPixel(x, y);
                    //MessageBox.Show(pixel.ToArgb().ToString());
 
                    int deltaR = Math.Abs(pixel.R - firstPixel.R);
                    int deltaG = Math.Abs(pixel.G - firstPixel.G);
                    int deltaB = Math.Abs(pixel.B - firstPixel.B);
                    int deltaTotal = deltaR + deltaG + deltaB;
 
                    if (deltaTotal > 500 || deltaTotal < -500)
                    {
                        darkLine = false;
                        break;
                    }
 
                }
                diffLine++;
                if (!darkLine) // 如果这一行和第一行不同，记录下这一行的行数
                {
                    break;
                }
            }
 
            if (diffLine == 0) // 如果所有行都相同
            {
                return image;
            }
            else // 如果有不同的行
            {
                return CropBitmap(image, 0, 0, diffLine, 0);
            }
        }
 
        // 去除右边黑边
        private Bitmap RemoveRightBlackEdge(Bitmap image)
        {
            int height = image.Height;
            int width = image.Width;
 
            Color firstPixel = image.GetPixel(width - 1, 0); // 获取右上角第一个像素的颜色
 
            int diffLine = 0; // 右边黑边列数
 
            for (int x = width - 1; x > 0; x--) // 从右边第一列开始比较
            {
                bool darkLine = true;
                for (int y = 0; y < height; y++)
                {
                    Color pixel = image.GetPixel(x, y);
                    //MessageBox.Show(pixel.ToArgb().ToString());
 
                    int deltaR = Math.Abs(pixel.R - firstPixel.R);
                    int deltaG = Math.Abs(pixel.G - firstPixel.G);
                    int deltaB = Math.Abs(pixel.B - firstPixel.B);
                    int deltaTotal = deltaR + deltaG + deltaB;
 
                    if (deltaTotal > 500 || deltaTotal < -500)
                    {
                        //MessageBox.Show(pixel.ToArgb().ToString() + firstPixel.ToArgb().ToString());
                        darkLine = false;
                        break;
                    }
 
                }
                diffLine++;
                if (!darkLine) // 如果这一列和第一列不同，记录下这一列的序号
                {
                    break;
                }
            }
 
            if (diffLine == 0) // 如果所有行都相同
            {
                return image;
            }
            else // 如果有不同的行
            {
                return CropBitmap(image, 0, 0, 0, diffLine);
            }
        }
}