好的,解决问题的两个部分。
以下代码显示了如何获取位图中的像素,更改它们并将它们放回位图中。你总是可以生成一个正确大小和格式的虚拟位图,打开它,复制你的数据,然后你就有一个包含数据的位图对象:
private void LockUnlockBitsExample(PaintEventArgs e)
{
// Create a new bitmap.
Bitmap bmp = new Bitmap("c:\\fakePhoto.jpg");
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
System.Drawing.Imaging.BitmapData bmpData =
bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
bmp.PixelFormat);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Declare an array to hold the bytes of the bitmap.
int bytes = bmpData.Stride * bmp.Height;
byte[] rgbValues = new byte[bytes];
// Copy the RGB values into the array.
System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);
// Set every third value to 255. A 24bpp bitmap will look red.
for (int counter = 2; counter < rgbValues.Length; counter += 3)
rgbValues[counter] = 255;
// Copy the RGB values back to the bitmap
System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);
// Unlock the bits.
bmp.UnlockBits(bmpData);
// Draw the modified image.
e.Graphics.DrawImage(bmp, 0, 150);
}
要将内容转换为 8bpp,您需要使用 System.Drawing.Imaging.ColorMatrix 类。我手头没有半色调的正确矩阵值,但是这个例子的灰度和值的调整应该让您了解效果:
Graphics g = e.Graphics;
Bitmap bmp = new Bitmap("sample.jpg");
g.FillRectangle(Brushes.White, this.ClientRectangle);
// Create a color matrix
// The value 0.6 in row 4, column 4 specifies the alpha value
float[][] matrixItems = {
new float[] {1, 0, 0, 0, 0},
new float[] {0, 1, 0, 0, 0},
new float[] {0, 0, 1, 0, 0},
new float[] {0, 0, 0, 0.6f, 0},
new float[] {0, 0, 0, 0, 1}};
ColorMatrix colorMatrix = new ColorMatrix(matrixItems);
// Create an ImageAttributes object and set its color matrix
ImageAttributes imageAtt = new ImageAttributes();
imageAtt.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
// Now draw the semitransparent bitmap image.
g.DrawImage(bmp, this.ClientRectangle, 0.0f, 0.0f, bmp.Width, bmp.Height,
GraphicsUnit.Pixel, imageAtt);
imageAtt.Dispose();
稍后我将尝试使用半色调的矩阵值进行更新,其中可能有很多 0.5 或 0.333 值!