maui-linux/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issu.../Bugzilla31029.cs

129 строки
3.8 KiB
C#

using System;
using System.IO;
using System.Text;
using Xamarin.Forms.CustomAttributes;
#if UITEST
using Xamarin.UITest;
using NUnit.Framework;
#endif
namespace Xamarin.Forms.Controls
{
[Preserve (AllMembers = true)]
[Issue (IssueTracker.Bugzilla, 31029, "[Windows Phone 8.1]Generating an Image via MemoryStream does not appear")]
public class Bugzilla31029 : TestContentPage // or TestMasterDetailPage, etc ...
{
protected override void Init ()
{
var generatedImage = new Image { Aspect = Aspect.AspectFit };
var btn = new Button { Text="generate" };
btn.Clicked += (sender, e) => {
var source = GenerateBmp (60, 60, Color.Red);
generatedImage.Source = source;
};
Content = new StackLayout {
Children = {
btn,
#pragma warning disable 618
new Label {Text = "GeneratedImage", Font=Font.BoldSystemFontOfSize(NamedSize.Medium)},
#pragma warning restore 618
generatedImage
},
Padding = new Thickness (0, 20, 0, 0),
VerticalOptions = LayoutOptions.StartAndExpand,
HorizontalOptions = LayoutOptions.CenterAndExpand
};
}
public ImageSource GenerateBmp (int rows, int cols, Color color)
{
BmpMaker bmpMaker = new BmpMaker (rows, cols);
//background color to white
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
bmpMaker.SetPixel (i, j, Color.White);
}
}
//draw a square
int marginX = rows / 10;
int marginY = cols / 10;
for (int row = marginX; row < (rows - marginX); row++) {
for (int col = marginY; col < (cols - marginY); col++) {
bmpMaker.SetPixel (row, col, color);
}
}
ImageSource resultImage = bmpMaker.Generate ();
return resultImage;
}
}
public class BmpMaker
{
const int HeaderSize = 54;
readonly byte[] _buffer;
public BmpMaker (int width, int height)
{
Width = width;
Height = height;
int numPixels = Width * Height;
int numPixelBytes = 4 * numPixels;
int fileSize = HeaderSize + numPixelBytes;
_buffer = new byte[fileSize];
// Write headers in MemoryStream and hence the buffer.
using (MemoryStream memoryStream = new MemoryStream (_buffer)) {
using (BinaryWriter writer = new BinaryWriter (memoryStream, Encoding.UTF8)) {
// Construct BMP header (14 bytes).
writer.Write (new char[] { 'B', 'M' }); // Signature
writer.Write (fileSize); // File size
writer.Write ((short) 0); // Reserved
writer.Write ((short) 0); // Reserved
writer.Write (HeaderSize); // Offset to pixels
// Construct BitmapInfoHeader (40 bytes).
writer.Write (40); // Header size
writer.Write (Width); // Pixel width
writer.Write (Height); // Pixel height
writer.Write ((short) 1); // Planes
writer.Write ((short) 32); // Bits per pixel
writer.Write (0); // Compression
writer.Write (numPixelBytes); // Image size in bytes
writer.Write (0); // X pixels per meter
writer.Write (0); // Y pixels per meter
writer.Write (0); // Number colors in color table
writer.Write (0); // Important color count
}
}
}
public int Width { get; private set; }
public int Height { get; private set; }
public void SetPixel (int row, int col, Color color)
{
SetPixel (row, col, (int) (255 * color.R),
(int) (255 * color.G),
(int) (255 * color.B),
(int) (255 * color.A));
}
public void SetPixel (int row, int col, int r, int g, int b, int a = 255)
{
int index = (row * Width + col) * 4 + HeaderSize;
_buffer[index + 0] = (byte) b;
_buffer[index + 1] = (byte) g;
_buffer[index + 2] = (byte) r;
_buffer[index + 3] = (byte) a;
}
public ImageSource Generate ()
{
Stream memoryStream = new MemoryStream (_buffer);
ImageSource imageSource = ImageSource.FromStream (() => { return memoryStream; });
return imageSource;
}
}
}