如果加载的图像来自资源，如何在图片框中放置边框颜色？

Question

I set my pictureBox with a default image from resources with this:

public Form1()
{
    InitializeComponent();
    pictureBox1.Image = Properties.Resources.default_Employee_Image;
}

when I check if the picture in the pictureBox is from resources with this code, it doesn't draw the border:

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    //pictureBox border color
    Color themeColor = Color.FromArgb(172, 188, 212);

    if (pictureBox1.Image == null) //if image from db is null display default image
    {
        pictureBox1.Image = Properties.Resources.default_Employee_Image;
    }

    //if image is the default image: paint border
    if (pictureBox1.Image == Properties.Resources.default_Employee_Image)
    {
        ControlPaint.DrawBorder(e.Graphics, pictureBox1.ClientRectangle, themeColor, ButtonBorderStyle.Solid);         
    }
}

Also if image from the pictureBox is default, I'll save it as null in my database.

I want to only have a border if the default image is loaded. If I select another image the border should be gone.

If the pictureBox has the default image it should look like this (which means that I still have not selected a picture of the user):

But if the picture in my pictureBox is not the default image-(the image in my resources), [This means that I already selected an image] it should look like this:

And not like this:

Answer 1

pictureBox1.Image == Properties.Resources.SomeImage will never return true , because every time that you call Properties.Resources.SomeImage , it returns a new instance of the image.

You don't need to track the assigned image; instead, you need to track the status . You can use either of the following options:

• Rely on a flag: You can set a flag like bool isDefaultImage = true; at form level and if at some point of your application you changed the image, set it to true. Something like this:

   if(isDefaultImage) { //draw border }

• Rely on Model/DataSource: You can also rely on your model/data source values and instead of checking UI elements, check if the user has a profile picture. Something like this:

   if(myUserObject.ProfilePicture == null) { //draw border }

Compare two images

Anyhow, just in case you are interested to compare two Image objects to see whether they are same Image, you can use the following method:

public bool AreImagesEqual(Image img1, Image img2)
{
    ImageConverter converter = new ImageConverter();
    byte[] bytes1 = (byte[])converter.ConvertTo(img1, typeof(byte[]));
    byte[] bytes2 = (byte[])converter.ConvertTo(img2, typeof(byte[]));
    return Enumerable.SequenceEqual(bytes1, bytes2);
}

Then you can use it like this:

using(var image = Properties.Resources.DefaultImage)
{
    var isDefaultImage = AreImagesEqual(pictureBox1.Image, image);
    if(isDefaultImage)
    {
        //draw border 
     }
}

Answer 2

I have found a solution for my problem, I have changed my approach (Rely on a flag approach [by @Reza Aghaei]), and instead of comparing pictureBox image with the resource image, I just checked if pictureBox1.Tag is null or not:

On my constructor:

public Form1()
{
    InitializeComponent();
    pictureBox1.Image = Properties.Resources.default_Employee_Image; //the default image from resources
    pictureBox1.Image = null;
}

On my dataGridView cell click event:

private void dataGridView_CellClick(object sender, DataGridViewCellEventArgs e)
{
    try
    {
        if (e.RowIndex != -1)
        {
            //Display user image
            using (SqlConnection con = new SqlConnection(connectionStringConfig))
            using (SqlCommand sqlCmd = new SqlCommand("SELECT user_image FROM dbo.Employee_Image WHERE employee_id=@employee_id", con))
            {
                con.Open();
                sqlCmd.Parameters.Add("@employee_id", SqlDbType.NVarChar).Value = EmployeeId;

                using (SqlDataReader reader = sqlCmd.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        reader.Read();
                        pictureBox1.Image = ImageOperations.BytesToImage((byte[])(reader.GetValue(0)));
                        if (reader.GetValue(0) == null) //if image is null add border color to tag
                        {
                            pictureBox1.Tag = my_color_here;
                        }
                        else
                        {
                            pictureBox1.Tag = null;
                        }
                    }
                    else
                    {
                        pictureBox1.Image = null;
                    }
                }
            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show($"Something is wrong with the selected record! \nError: { ex.GetType().FullName }");
    }
}

On BytesToImage method in ImageOperations class:

public static Image BytesToImage(byte[] buffer) //Get image from database
{
    using (MemoryStream ms = new MemoryStream(buffer))
    {
        return Image.FromStream(ms);
    }
}

And on my pictureBox paint event:

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    //if image is not present in the picturebox -> paint its border
    if (pictureBox1.Image == null)
    {
        pictureBox1.Tag = my_color_here;
        pictureBox1.Image = Properties.Resources.default_Employee_Image;
    }

    if (pictureBox1.Tag != null) //if tag has a value -> paint the border (this happens if image form db is null)
    {
        ControlPaint.DrawBorder(e.Graphics, pictureBox1.ClientRectangle, my_color_here, ButtonBorderStyle.Solid);
    }
}