C＃/ WPF位图仍然是白色设置一些值（带LockBits）后， [英] C# / WPF Bitmap remains white after setting some values (with LockBits)
问题描述
使用MS Visual Studio的2013年，有这个代码：
Using MS Visual Studio 2013, having this code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Drawing;
using System.Drawing.Imaging;
namespace SplashNS
{
public partial class DocumentWindow : Window
{
public SplashFile File;
[DllImport("gdi32")]
static extern int DeleteObject(IntPtr o);
private BitmapSource _loadBitmap(System.Drawing.Bitmap source)
{
IntPtr ip = source.GetHbitmap();
BitmapSource bs = null;
try
{
bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(ip,
IntPtr.Zero, Int32Rect.Empty,
System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
}
finally
{
DeleteObject(ip);
}
return bs;
}
public DocumentWindow()
{
InitializeComponent();
Bitmap canvas = new Bitmap(663, 356);
BitmapData bmd = canvas.LockBits(new System.Drawing.Rectangle(0, 0, canvas.Width, canvas.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, canvas.PixelFormat);
int PixelSize = 4;
unsafe
{
for (int y = 0; y < canvas.Height; y++)
{
byte* row = (byte*)bmd.Scan0 + (y * bmd.Stride);
for (int x = 0; x < canvas.Width; x++)
{
row[x * PixelSize] = 255;
}
}
}
canvas.UnlockBits(bmd);
SplashCanvas.Source = this._loadBitmap(canvas);
}
}
}
不起作用。它生成一个白色的位图，而不是一个与所有蓝色像素。不显示错误。
doesn't work. It generates a white bitmap instead of one with all blue pixels. No errors are displayed.
我想，那一定是一个小白的问题，但我是一个初学者。我想这一定有什么用像素格式，但我也可以错...
I guess, it must be a noob issue, but I am a beginner. I suppose it must be something with the pixel format, but I can also be wrong with that...
推荐答案
您似乎是创造一个老式的 System.Drawing.Bitmap 然后将其转换为WPF，但是WPF已使用的 WritableBitmap 。看到这篇文章的概述：基础：位图和像素位
You seem to be creating an old-style System.Drawing.Bitmap then converting it to WPF, however WPF has a pretty complete set of utilities for creating bitmaps from scratch using WritableBitmap. See this article for an overview: Foundations: Bitmaps and Pixel Bits.
例如，下面是一个创建一个给定的大小和颜色的固位代码：
For instance, here's code that creates a solid bitmap of a given size and color:
public static class BitmapHelper
{
public unsafe static BitmapSource CreateSolidBitmap(int width, int height, double dpiX, double dpiY, Color color)
{
var bitmap = new WriteableBitmap(width, height, dpiX, dpiY, PixelFormats.Pbgra32, null);
var format = bitmap.Format;
int blueIndex, greenIndex, redIndex, alphaIndex;
int bitsPerPixel, bytesPerPixel;
if (!TryParsePixelFormat(format, out bitsPerPixel, out bytesPerPixel, out blueIndex, out greenIndex, out redIndex, out alphaIndex))
return null;
var byteWidth = bytesPerPixel * width;
bitmap.Lock();
try
{
var backBuffer = (byte*)bitmap.BackBuffer.ToPointer();
for (int iRow = 0; iRow < height; iRow++)
{
var row = backBuffer + (iRow * bitmap.BackBufferStride);
for (byte* pixel = row, endRow = row + byteWidth; pixel < endRow; pixel += bytesPerPixel)
{
pixel[blueIndex] = color.B;
pixel[greenIndex] = color.G;
pixel[redIndex] = color.R;
if (alphaIndex >= 0)
pixel[alphaIndex] = color.A;
}
}
bitmap.AddDirtyRect(new Int32Rect(0, 0, width, height));
}
finally
{
bitmap.Unlock();
}
return bitmap;
}
static int BlueIndex = 0;
static int GreenIndex = 1;
static int RedIndex = 2;
static int AlphaIndex = 3;
private static bool TryFindColorIndex(PixelFormatChannelMask mask, out int index)
{
var maskList = mask.Mask;
for (int i = 0, count = maskList.Count; i < count; i++)
{
if (maskList[i] == 255)
{
index = i;
return true;
}
}
index = -1;
return false;
}
static bool TryParsePixelFormat(PixelFormat format, out int bitsPerPixel, out int bytesPerPixel, out int blueIndex, out int greenIndex, out int redIndex, out int alphaIndex)
{
// Currently only implemented for non-indexed formats with 3 or 4 bytes
// per color.
bitsPerPixel = format.BitsPerPixel;
if ((bitsPerPixel % 8) != 0)
{
bytesPerPixel = blueIndex = greenIndex = redIndex = alphaIndex = -1;
return false;
}
bytesPerPixel = bitsPerPixel / 8;
var masks = format.Masks;
int maskCount = masks.Count;
if (maskCount == 3 || maskCount == 4)
{
var blueMask = masks[BlueIndex];
var greenMask = masks[GreenIndex];
var redMask = masks[RedIndex];
if (!TryFindColorIndex(blueMask, out blueIndex)
|| !TryFindColorIndex(greenMask, out greenIndex)
|| !TryFindColorIndex(redMask, out redIndex))
{
bytesPerPixel = blueIndex = greenIndex = redIndex = alphaIndex = -1;
return false;
}
if (maskCount == 3)
{
alphaIndex = -1;
}
else
{
if (!TryFindColorIndex(masks[AlphaIndex], out alphaIndex))
alphaIndex = -1;
}
return true;
}
bytesPerPixel = blueIndex = greenIndex = redIndex = alphaIndex = -1;
return false;
}
}
由于这是一个静态方法，它不知道在DPI为您运行的应用程序，但是你可以得到它的主窗口内（或任何其他窗口）是这样的：
Since this is a static method it doesn't know the DPI for your running application, however you can get it inside your main window (or any other window) like this:
PresentationSource source = PresentationSource.FromVisual(this);
double dpiX = 96.0, dpiY = 96.0;
if (source != null)
{
dpiX = 96.0 * source.CompositionTarget.TransformToDevice.M11;
dpiY = 96.0 * source.CompositionTarget.TransformToDevice.M22;
}
96似乎习惯于按照惯例时，这是不可用的。
96 seems to get used by convention when this is not available.
这篇关于C＃/ WPF位图仍然是白色设置一些值（带LockBits）后，的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
