c# - 使用 C# 从 BitmapData 裁剪区域

Question

我有一个位图sourceImage.bmp

锁定它的位:

BitmapData dataOriginal = sourceImage.LockBits(new Rectangle(0, 0, sourceImage.Width, sourceImage.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

进行分析，克隆:

Bitmap originalClone = AForge.Imaging.Image.Clone(dataOriginal);

解锁位:

sourceImage.UnlockBits(dataOriginal);

是否可以指定要复制“dataOriginal”的哪一部分 (x,y,w,h)？或者从 dataOriginal 创建新数据，指定 X 和 Y 坐标以及 H 和 W？

目的是从此图像中复制一个小区域。此方法可能比 DrawImage 更快，这就是我不使用后者的原因。

编辑:

所以我使用了29 Mb 位图并做了一些硬核测试!全尺寸裁剪(基本上是副本)+ 100 次迭代。

代码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using AForge;
using AForge.Imaging;
using System.Diagnostics;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices;


namespace testCropClone
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private unsafe Bitmap Clone(Bitmap bmp, int startX, int startY, int width, int height)
        {
        Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
        BitmapData rawOriginal = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

        int origByteCount = rawOriginal.Stride * rawOriginal.Height;
        byte[] origBytes = new Byte[origByteCount];
        Marshal.Copy(rawOriginal.Scan0, origBytes, 0, origByteCount);

        int BPP = 4;        //4 Bpp = 32 bits, 3 = 24, etc.

        byte[] croppedBytes = new Byte[width * height * BPP];

        //Iterate the selected area of the original image, and the full area of the new image
        for (int i = 0; i < height; i++)
        {
            for (int j = 0; j < width * BPP; j += BPP)
            {
                int origIndex = (startX * rawOriginal.Stride) + (i * rawOriginal.Stride) + (startY * BPP) + (j);
                int croppedIndex = (i * width * BPP) + (j);

                //copy data: once for each channel
                for (int k = 0; k < BPP; k++)
                {
                    croppedBytes[croppedIndex + k] = origBytes[origIndex + k];
                }
            }
        }

        //copy new data into a bitmap
        Bitmap croppedBitmap = new Bitmap(width, height);
        BitmapData croppedData = croppedBitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
        Marshal.Copy(croppedBytes, 0, croppedData.Scan0, croppedBytes.Length);

        bmp.UnlockBits(rawOriginal);
        croppedBitmap.UnlockBits(croppedData);

        return croppedBitmap;
        }

        private Bitmap cloneBitmap(Bitmap bmp, int startX, int startY, int width, int height)
        {
            Rectangle srcRect = Rectangle.FromLTRB(startX, startY, width, height);
            Bitmap cloneBitmap = bmp.Clone(srcRect, bmp.PixelFormat);
            return cloneBitmap;
        }


        private Bitmap cloneRectangle(Bitmap bmp, int startX, int startY, int width, int height)
        {
            Rectangle srcRect = Rectangle.FromLTRB(startX, startY, width, height);
            Bitmap dest = new Bitmap(srcRect.Width, srcRect.Height);
            Rectangle destRect = new Rectangle(0, 0, srcRect.Width, srcRect.Height);
            using (Graphics graphics = Graphics.FromImage(dest))
            {
                graphics.DrawImage(bmp, destRect, srcRect, GraphicsUnit.Pixel);
            }
            return dest;
        }


        private Bitmap cloneAforge(Bitmap bmp, int startX, int startY, int width, int height)
        {
            BitmapData rawOriginal = bmp.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            Bitmap cloneBitmap = AForge.Imaging.Image.Clone(rawOriginal);
            bmp.UnlockBits(rawOriginal);
            return cloneBitmap;
        }



        private void button1_Click(object sender, EventArgs e)
        {
            Bitmap source = new Bitmap(@"C:\9\01.bmp");

            Stopwatch s1 = Stopwatch.StartNew();
            for (int i = 0; i < 100; i++)
            {
                Bitmap Clone1 = cloneAforge(source, 0, 0, source.Width, source.Height);
                Clone1.Dispose();

            }

            /*Bitmap Clone1 = cloneAforge(source, 0, 0, source.Width, source.Height);
            Clone1.Save(@"C:\9\01_aforge.bmp");
            Clone1.Dispose();*/

            s1.Stop();
            source.Dispose();
            textBox1.Text = ("" + s1.ElapsedMilliseconds / 100 + " ms");
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Bitmap source = new Bitmap(@"C:\9\01.bmp");

            Stopwatch s1 = Stopwatch.StartNew();
            for (int i = 0; i < 100; i++)
            {
                Bitmap Clone1 = cloneBitmap(source, 0, 0, source.Width, source.Height);
                Clone1.Dispose();

            }

            /*Bitmap Clone1 = cloneBitmap(source, 0, 0, source.Width, source.Height);
            Clone1.Save(@"C:\9\01_bitmap.bmp");
            Clone1.Dispose();*/

            s1.Stop();


            source.Dispose();
            textBox2.Text = ("" + s1.ElapsedMilliseconds / 100 + " ms");
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Bitmap source = new Bitmap(@"C:\9\01.bmp");

            Stopwatch s1 = Stopwatch.StartNew();
            for (int i = 0; i < 100; i++)
            {
                Bitmap Clone1 = Clone(source, 0, 0, source.Width, source.Height);
                Clone1.Dispose();

            }

            /*Bitmap Clone1 = Clone(source, 0, 0, source.Width, source.Height);
            Clone1.Save(@"C:\9\01_bits.bmp");
            Clone1.Dispose();*/

            s1.Stop();
            source.Dispose();
            textBox3.Text = ("" + s1.ElapsedMilliseconds / 100 + " ms");
        }

        private void button4_Click(object sender, EventArgs e)
        {
            Bitmap source = new Bitmap(@"C:\9\01.bmp");

            Stopwatch s1 = Stopwatch.StartNew();
            for (int i = 0; i < 100; i++)
            {
                Bitmap Clone1 = cloneRectangle(source, 0, 0, source.Width, source.Height);
                Clone1.Dispose();

            }


            /*Bitmap Clone1 = cloneRectangle(source, 0, 0, source.Width, source.Height);
            Clone1.Save(@"C:\9\01_rect.bmp");
            Clone1.Dispose();*/


            s1.Stop();
            source.Dispose();
            textBox4.Text = ("" + s1.ElapsedMilliseconds / 100 + " ms");
        }
    }
}

Edit2:(Aforge 全尺寸裁剪..)方法 Nr. 2

        for (int i = 0; i < 100; i++)
        {
            Crop crop = new Crop(new Rectangle(0, 0, source.Width, source.Height));
            var source2 = crop.Apply(source);
            source2.Dispose();

        }

平均 = 62 毫秒(比第一种 Aforge 方法少 40 毫秒)

结果:

1. 位图克隆(0 毫秒)?? (作弊，不是吗？)
2. Aforge #2(65 毫秒)
3. Aforge #1(105 毫秒)
4. 矩形(170 毫秒)
5. 锁定位(803 毫秒)(等待修复/新测试结果..)

Answer 1

我提出了一个快速(而且公认的粗糙)的手动解决方案，演示了如何使用锁定的位图来执行此操作。它应该比替代方法快得多，但确实涉及更多代码。

        Bitmap bmp = new Bitmap(@"C:\original.jpg");
        Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
        BitmapData rawOriginal = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

        int origByteCount = rawOriginal.Stride * rawOriginal.Height;
        byte[] origBytes = new Byte[origByteCount];
        Marshal.Copy(rawOriginal.Scan0, origBytes, 0, origByteCount);

        //I want to crop a 100x100 section starting at 15, 15.
        int startX = 15;
        int startY = 15;
        int width = 100;
        int height = 100;
        int BPP = 4;        //4 Bpp = 32 bits, 3 = 24, etc.

        byte[] croppedBytes = new Byte[width * height * BPP];

        //Iterate the selected area of the original image, and the full area of the new image
        for (int i = 0; i < height; i++)
        {
            for (int j = 0; j < width * BPP; j += BPP)
            {
                int origIndex = (startX * rawOriginal.Stride) + (i * rawOriginal.Stride) + (startY * BPP) + (j);
                int croppedIndex = (i * width * BPP) + (j);

                //copy data: once for each channel
                for (int k = 0; k < BPP; k++)
                {
                    croppedBytes[croppedIndex + k] = origBytes[origIndex + k];
                }
            }
        }

        //copy new data into a bitmap
        Bitmap croppedBitmap = new Bitmap(width, height);
        BitmapData croppedData = croppedBitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
        Marshal.Copy(croppedBytes, 0, croppedData.Scan0, croppedBytes.Length);

        bmp.UnlockBits(rawOriginal);
        croppedBitmap.UnlockBits(croppedData);

        croppedBitmap.Save(@"C:\test.bmp");

我使用了这张原始图片:

要输出此图像，裁剪为 100x100 @ 15,15:

显然，如果您使用此代码，您需要稍微清理一下并添加错误处理。如果我正确理解您的问题，那么以这种方式做事应该完全不需要使用 AForge。