创建图像掩码 [英] Create Image Mask

问题描述

用户提供了我的应用程序的图像，从这些应用程序需要做一个面膜：

The user provides my app an image, from which the app needs to make a mask:

掩模包含一个红色像素在原始图像中的每个透明象素

The mask contains a red pixel for each transparent pixel in the original image.

我试过如下：

Bitmap OrgImg = Image.FromFile(FilePath);
Bitmap NewImg = new Bitmap(OrgImg.Width, OrgImg.Height);
for (int y = 0; y <= OrgImg.Height - 1; y++) {
    for (int x = 0; x <= OrgImg.Width - 1; x++) {
        if (OrgImg.GetPixel(x, y).A != 255) {
            NewImg.SetPixel(x, y, Color.FromArgb(255 - OrgImg.GetPixel(x, y).A, 255, 0, 0));
        }
    }
}
OrgImg.Dispose();
PictureBox1.Image = NewImg;

我很担心在慢的电脑的性能。有没有更好的方法来做到这一点？

I am worried about the performance on slow PCs. Is there a better approach to do this?

推荐答案

这是完全可以接受的使用与getPixel（）如果只是零星使用，例如：上加载一个图像。但是，如果你想要做一个更严重的图像处理，最好是直接的的BitmapData 。一个小例子：

It is perfectly acceptable to use GetPixel() if it is only used sporadicly, e.g. on loading one image. However, if you want to do a more serious image processing, it is better to work directly with BitmapData. A small example:

//Load the bitmap
Bitmap image = (Bitmap)Image.FromFile("image.png"); 

//Get the bitmap data
var bitmapData = image.LockBits (
    new Rectangle (0, 0, image.Width, image.Height),
    ImageLockMode.ReadWrite, 
    image.PixelFormat
);

//Initialize an array for all the image data
byte[] imageBytes = new byte[bitmapData.Stride * image.Height];

//Copy the bitmap data to the local array
Marshal.Copy(bitmapData.Scan0,imageBytes,0,imageBytes.Length);

//Unlock the bitmap
image.UnlockBits(bitmapData);

//Find pixelsize
int pixelSize = Image.GetPixelFormatSize(image.PixelFormat);

// An example on how to use the pixels, lets make a copy
int x = 0;
int y = 0;
var bitmap = new Bitmap (image.Width, image.Height);

//Loop pixels
for(int i=0;i<imageBytes.Length;i+=pixelSize/8)
{
    //Copy the bits into a local array
    var pixelData = new byte[3];
    Array.Copy(imageBytes,i,pixelData,0,3);

    //Get the color of a pixel
    var color = Color.FromArgb (pixelData [0], pixelData [1], pixelData [2]);

    //Set the color of a pixel
    bitmap.SetPixel (x,y,color);

    //Map the 1D array to (x,y)
    x++;
    if( x >= 100)
    {
        x=0;
        y++;
    }

}

//Save the duplicate
bitmap.Save ("image_copy.png");

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