Why is setpixel so slow?

Why is setpixel so slow?

• VShaneCurtis

  I have since discovered that the .exe file produced by VB2005 runs at an acceptable speed. It is only when running the program in debugging mode that setpixel is so slow. Other graphics routines are slowed down by a certain anmount when debugging but nothing like as much as setpixel. Can anyone explain Is anyone else out there using setpixel under VB2005

  Here is the code I am using.

  Imports System.Drawing.Drawing2D

  Public Class Form1

  'This example fills a 400x400 pixel bitmap with colour

  'When run in debugging mode

  'the SetPixel method takes over 6 seconds

  'the FillRectangle mathod takes 2.5 seconds

  'Why is the former slower than the latter and why are they both so slow

  'When the exe file is run directly, both routines take less than half a second and setpixel is faster

  Dim start, finish As Double

  Dim n, x, y As Integer

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

  n = 400

  Dim bm1 As New Bitmap(n, n)

  Dim bm2 As New Bitmap(n, n)

  start = Microsoft.VisualBasic.DateAndTime.Timer

  For y = 0 To n - 1

  For x = 0 To n - 1

  bm1.SetPixel(x, y, Color.Blue)

  Next

  Next

  finish = Microsoft.VisualBasic.DateAndTime.Timer

  TextBox1.Text = Str((finish - start) * 1000)

  PictureBox1.BackgroundImage = bm1

  Dim gr As Graphics

  gr = Graphics.FromImage(bm2)

  start = Microsoft.VisualBasic.DateAndTime.Timer

  For y = 0 To n - 1

  For x = 0 To n - 1

  gr.FillRectangle(Brushes.Red, x, y, 1, 1)

  Next

  Next

  finish = Microsoft.VisualBasic.DateAndTime.Timer

  TextBox2.Text = Str((finish - start) * 1000)

  PictureBox2.BackgroundImage = bm2

  End Sub

  End Class

  
  
• Why is setpixel so slow?