Advice needed please - How to display an image from a file quickly?

The problem is SetPixel. The stream may be a bottleneck after you fix the SetPixel problem. Here is a class for extremely fast bitmap processing, without using unsafe code -- actually it seems to be faster than unsafe.

We are using the 32bppPARGB format as this is the format ultimately used internally by GDI+. It is the fastest format. For each integer in the Integers array, the most significant byte is the alpha, followed by the red byte, then green, then blue. So to get the alpha: value >> 24. To get the red: (value >> 16) & 0xFF.

using System; using System.Collections; using System.ComponentModel; using System.Drawing; using System.Drawing.Drawing2D; using System.Drawing.Imaging; using System.Windows.Forms; using System.Runtime.InteropServices; internal sealed class EffectBuffer { private uint[] ints; private GCHandle handle; private Bitmap bitmap; public EffectBuffer(int bufferWidth, int bufferHeight) { AllocateBitmap(bufferWidth, bufferHeight); } public void AllocateBitmap(int width, int height) { if (Width == width && Height == height) return; DisposeBitmap(); if (width == 0 || height == 0) return; // 4 bytes per pixel, format: ARGB ints = new uint[width * height]; // if not pinned the GC can move around the array handle = GCHandle.Alloc(ints, GCHandleType.Pinned); IntPtr pointer = Marshal.UnsafeAddrOfPinnedArrayElement(ints, 0); bitmap = new Bitmap(width , height, width * 4, PixelFormat.Format32bppPArgb, pointer); } public void Dispose() { DisposeBitmap(); } private void DisposeBitmap() { if (bitmap != null) { handle.Free(); bitmap.Dispose(); bitmap = null; ints = null; } } /// <summary> /// A bitmap that can be rendered upon, or rendered to another graphics. /// </summary> public Bitmap Bitmap { get { return bitmap; } } /// <summary>Width of <see cref="Bitmap"/>.</summary> public int Width { get { return bitmap == null ? 0 : bitmap.Width; } } /// <summary>Height of <see cref="Bitmap"/>.</summary> public int Height { get { return bitmap == null ? 0 : bitmap.Height; } } /// <summary> /// The integers that make up the pixels in <see cref="Bitmap"/>. The /// pixels can be modified directly by modifying this array. /// The pixels must contain premuliplied ARGB: R, G, and B /// components cannot be larger than the A component. /// </summary> public uint[] Integers { get { return ints; } } }

FrankHileman at 2007-9-9 >

Firstly this is only of interest if you have lots of small bitmaps -- 85K is small. Secondly you would have to prevent fragmentation within your own array. So I don't see a big advantage, but I thow the idea out there anyway.

FrankHileman at 2007-9-9 >

Hi,

I got a similar problem: I have to show a sequence of bitmaps from the hard disk on the display for simulation purpose.

This job must be done in a minimum of time, because the main issue is the analysis of the shown content. So I found your thread..

My question is: how can I make my program using one and the same part of memory each time a new bitmap is loaded? This is necessary due to avoiding out-of-memory exceptions and due to increasing speed. All the pictures have the same size and pixelformat.

So maybe you know a way to realize it using managed code (programming in C++/CLI ...but understanding C# too)

Thanks

Staehff

Staehff at 2007-9-9 >