Have not done this before (except in java, look how Steve McLeod fixed it), so obviously I suck at it. Here 64 pixels around current mouse position get drawn little bigger on a form. Problem is, that it's 'kind of' to slow, and I have no idea where to start fixing.
Besides that, I made a timer thread, that constantly calls update graphics when it's finished and a little fps like text, to show really how fast things are drawn.
Image example: (Image is from letter 'a' in "IntelliTrace" in Microsoft VS2010)
Source example:
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 System.Runtime.InteropServices;
namespace Zoom
{
public partial class Form1 : Form
{
static class dllRef
{
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetCursorPos(out Point lpPoint);
[DllImport("user32.dll")]
static extern IntPtr GetDC(IntPtr hwnd);
[DllImport("user32.dll")]
static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);
[DllImport("gdi32.dll")]
static extern uint GetPixel(IntPtr hdc, int nXPos, int nYPos);
// from http://www.pinvoke.net/default.aspx/gdi32/GetPixel.html
static public System.Drawing.Color getPixelColor(int x, int y) {
IntPtr hdc = GetDC(IntPtr.Zero);
uint pixel = GetPixel(hdc, x, y);
ReleaseDC(IntPtr.Zero, hdc);
Color color = Color.FromArgb((int)(pixel & 0x000000FF),
(int)(pixel & 0x0000FF00) >> 8,
(int)(pixel & 0x00FF0000) >> 16);
return color;
}
static public System.Drawing.Point getMousePosition() {
Point p = new Point();
GetCursorPos(out p);
return p;
}
}
public Form1() {
InitializeComponent();
this.Size = new Size(400,400);
this.Text="Image zoom";
this.Location = new Point(640, 0);
this.image = new Bitmap(320, 320);
this.timeRef = DateTime.Now;
this.BackColor = Color.White;
Timer t = new Timer();
t.Interval = 25;
t.Tick += new EventHandler(Timer_Tick);
t.Start();
}
public void Timer_Tick(object sender, EventArgs eArgs) {
this.Form1_Paint(this, new PaintEventArgs(this.CreateGraphics(), new Rectangle(0, 0, this.Width, this.Height)));
}
private bool isdone = true;
private int iter = 0;
private Bitmap image;
private DateTime timeRef;
private void Form1_Paint(object sender, PaintEventArgs e) {
if (isdone) {
isdone = false;
int step = 40;
Point p = dllRef.getMousePosition();
Pen myPen = new Pen(Color.Gray, 1);
SolidBrush myBrush = null;
Bitmap image2 = new Bitmap(320, 340);
Graphics gc = Graphics.FromImage(image2);
for (int x = 0; x < 8; x++) {
for (int y = 0; y < 8; y++) {
myBrush = new SolidBrush(dllRef.getPixelColor(p.X - 4 + x, p.Y - 4 + y));
gc.FillEllipse(myBrush, x * step, y * step, step - 3, step - 3);
gc.DrawEllipse(myPen, x * step, y * step, step - 3, step - 3);
}
}
StringBuilder sb = new StringBuilder();
sb.Append(iter)
.Append(" frames in ")
.Append(String.Format("{0:0.###}", ((DateTime.Now-this.timeRef).TotalMilliseconds)/1000))
.Append("s.");
gc.FillRectangle(new SolidBrush(this.BackColor), new Rectangle( 0, 320, 320, 40));
gc.DrawString(sb.ToString(),new Font("Arial", 12),new SolidBrush(Color.Black), 10, 320);
gc.Dispose();
isdone = true;
iter++;
image = image2;
}
e.Graphics.DrawImage(image, 35f, 15f);
}
}
}
After changes i made, this one is ~98% faster:
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 System.Runtime.InteropServices;
namespace Zoom
{
public partial class Form1 : Form
{
static class dllRef
{
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetCursorPos(out Point lpPoint);
[DllImport("user32.dll")]
static extern IntPtr GetDC(IntPtr hwnd);
[DllImport("user32.dll")]
static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);
[DllImport("gdi32.dll")]
static extern uint GetPixel(IntPtr hdc, int nXPos, int nYPos);
// from http://www.pinvoke.net/default.aspx/gdi32/GetPixel.html
static public System.Drawing.Color getPixelColor(int x, int y) {
IntPtr hdc = GetDC(IntPtr.Zero);
uint pixel = GetPixel(hdc, x, y);
ReleaseDC(IntPtr.Zero, hdc);
Color color = Color.FromArgb((int)(pixel & 0x000000FF),
(int)(pixel & 0x0000FF00) >> 8,
(int)(pixel & 0x00FF0000) >> 16);
return color;
}
static public System.Drawing.Point getMousePosition() {
Point p = new Point();
GetCursorPos(out p);
return p;
}
}
public Form1() {
InitializeComponent();
this.Size = new Size(400,400);
this.Text="Image zoom";
this.Location = new Point(640, 0);
this.image = new Bitmap(320, 340);
this.timeRef = DateTime.Now;
this.BackColor = Color.White;
Timer t = new Timer();
t.Interval = 25;
t.Tick += new EventHandler(Timer_Tick);
t.Start();
}
public void Timer_Tick(object sender, EventArgs eArgs) {
this.Form1_Paint(this, new PaintEventArgs(this.CreateGraphics(), new Rectangle(0, 0, this.Width, this.Height)));
}
private bool isdone = true;
private int iter = 0;
private Bitmap image;
private DateTime timeRef;
private void Form1_Paint(object sender, PaintEventArgs e) {
if (isdone) {
isdone = false;
int step = 40;
Point p = dllRef.getMousePosition();
SolidBrush myBrush = null;
Bitmap hc = new Bitmap(8, 8);
using (Pen myPen = new Pen(Color.Gray, 1))
using (Graphics gc = Graphics.FromImage(image))
using (Graphics gf = Graphics.FromImage(hc))
{
gf.CopyFromScreen(p.X - 4, p.Y - 4, 0, 0, new Size(8, 8),
CopyPixelOperation.SourceCopy);
for (int x = 0; x < 8; x++)
{
for (int y = 0; y < 8; y++)
{
myBrush = new SolidBrush(hc.GetPixel(x, y));
gc.FillEllipse(myBrush, x * step, y * step, step - 3, step - 3);
gc.DrawEllipse(myPen, x * step, y * step, step - 3, step - 3);
}
}
double ts = ((DateTime.Now - this.timeRef).TotalMilliseconds) / 1000;
StringBuilder sb = new StringBuilder();
sb.Append(++iter).Append(" frames in ").Append(String.Format("{0:0.###}", ts)).Append("s.");
gc.FillRectangle(new SolidBrush(this.BackColor), new Rectangle(0, 320, 320, 40));
gc.DrawString(sb.ToString(), new Font("Arial", 12), new SolidBrush(Color.Black), 10, 320);
}
isdone = true;
}
e.Graphics.DrawImage(image, 35f, 15f);
}
}
}
Jim Mischel
One thing that should speed things up is if you do the GetDC just once and get all of the pixels you need, then call ReleaseDC. So rather than:
for each pixel
GetDC
Read Pixel
ReleaseDC
You have:
GetDC
for each pixel
read pixel and store value
ReleaseDC
Then process the stored pixels.
That said, you're probably better off not using GetPixel at all, as I seem to remember it being terribly inefficient. I suspect you'd have better performance just grabbing the entire screen into a bitmap and getting the pixels from there. Perhaps the answer to this question will help you: Capture the Screen into a Bitmap
来源：https://stackoverflow.com/questions/3743897/how-to-draw-constantly-changing-graphics