Invalidate picturebox with rectangle on
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Hello. I have a simple picturebox where there is a image loaded in Im drawing a rectangle on the picturebox and when I press a button I want to invalidate it (remove the rectangle), but it doesnt seem to work The rectangle is drawn fine and the image loads up to, but when I press my button nothing happens Here is the code im using:
private void drawOnPic() { // Attach grapich to picturebox Graphics g = Graphics.FromImage(pictureBox1.Image); // Create a new pen that we shall use for drawing the line Pen PenStyle = new Pen(Color.Red, 1); // Draw a 50x50 pixels rectangle (x, y, width, hight) g.DrawRectangle(PenStyle, 20, 20, 50, 50); } private void button1_Click(object sender, EventArgs e) { pictureBox1.Invalidate(); } private void Form1_Load(object sender, EventArgs e) { drawOnPic(); } -
Hello. I have a simple picturebox where there is a image loaded in Im drawing a rectangle on the picturebox and when I press a button I want to invalidate it (remove the rectangle), but it doesnt seem to work The rectangle is drawn fine and the image loads up to, but when I press my button nothing happens Here is the code im using:
private void drawOnPic() { // Attach grapich to picturebox Graphics g = Graphics.FromImage(pictureBox1.Image); // Create a new pen that we shall use for drawing the line Pen PenStyle = new Pen(Color.Red, 1); // Draw a 50x50 pixels rectangle (x, y, width, hight) g.DrawRectangle(PenStyle, 20, 20, 50, 50); } private void button1_Click(object sender, EventArgs e) { pictureBox1.Invalidate(); } private void Form1_Load(object sender, EventArgs e) { drawOnPic(); }Hi,
Graphics.FromImage(pictureBox1.Image);gives you access to the internals of the image the PB is showing.g.DrawRectangle(...);modifies this image; such modification is irreversible, invalidating the PB only tells it to repaint itself, hence showing the modified image again. If you want to be able to undo graphic stuff, either paint on top of the PB (using its OnPaint handler) or keep a copy of the original image, so you can restore it (PB.Image=oldImage;). :)Luc Pattyn [Forum Guidelines] [My Articles]
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