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POField xxx is never assigned to, and will always have its default value null
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copied!<p>Anyone know whats this problem? </p> <p>I got this warning <strong>Field xxx is never assigned to, and will always have its default value null</strong> on <code>private static Quantizer <strong>quantit</strong>;</code></p> <p>I dont know what to do to fix, cause when I try to use <code>quantit.Quantize()</code> debug says: <strong>"Object reference not set to an instance of an object."</strong> and point to <code>au = quantit.Quantize();</code></p> <p>The code:</p> <pre><code>public class Quantization : System.Windows.Forms.Form { private static Quantizer quantit; private Button btnLoad; private PictureBox imgPhoto; public Quantization() { btnLoad = new Button(); btnLoad.Text = "&Load"; btnLoad.Left = 10; btnLoad.Top = 10; btnLoad.Click += new System.EventHandler(this.OnLoadClick); imgPhoto = new PictureBox(); imgPhoto.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D; imgPhoto.Width = this.Width / 2; imgPhoto.Height = this.Height / 2; imgPhoto.Left = (this.Width - imgPhoto.Width) / 2; imgPhoto.Top = (this.Height - imgPhoto.Height) / 2; imgPhoto.SizeMode = PictureBoxSizeMode.StretchImage; this.Controls.Add(btnLoad); this.Controls.Add(imgPhoto); } protected void OnLoadClick(object sender, System.EventArgs e) { OpenFileDialog dlg = new OpenFileDialog(); dlg.Title = "Open Image"; dlg.Filter = "jpg files (*.jpg)|*.jpg|All files (*.*)|*.*" ; if (dlg.ShowDialog() == DialogResult.OK) { Bitmap au; //Image bmp = Image.FromFile("D:\\Documents and Settings\\kiosk.suprisul\\My Documents\\foto1.jpg"); au = quantit.Quantize(); imgPhoto.Image = au; //imgPhoto.Image = bmp; //imgPhoto.Image = au; //new Bitmap(dlg.OpenFile()); } dlg.Dispose(); } [STAThread] static void Main(string[] args) { //Image bmp; //bmp = Image.FromFile("teste.jpg"); //PaintEventArgs e; //teste2.Quantize(bmp); Application.Run(new Quantization()); /* System.Console.WriteLine("Hello, World!"); System.Console.ReadLine();*/ } } </code></pre> <p>The class:</p> <pre><code>namespace ImageManipulation { public unsafe abstract class Quantizer { /// <summary> /// Construct the quantizer /// </summary> /// <param name="singlePass">If true, the quantization only needs to loop through the source pixels once</param> /// <remarks> /// If you construct this class with a true value for singlePass, then the code will, when quantizing your image, /// only call the 'QuantizeImage' function. If two passes are required, the code will call 'InitialQuantizeImage' /// and then 'QuantizeImage'. /// </remarks> public Quantizer(bool singlePass) { _singlePass = singlePass; } /// <summary> /// Quantize an image and return the resulting output bitmap /// </summary> /// <param name="source">The image to quantize</param> /// <returns>A quantized version of the image</returns> public Bitmap Quantize()//Image source) { Image source = Image.FromFile("C:\\Users\\crashboy\\Downloads\\image009.jpg"); // Get the size of the source image int height = source.Height; int width = source.Width; // And construct a rectangle from these dimensions Rectangle bounds = new Rectangle(0, 0, width, height); // First off take a 32bpp copy of the image Bitmap copy = new Bitmap(width, height, PixelFormat.Format32bppArgb); // And construct an 8bpp version Bitmap output = new Bitmap(width, height, PixelFormat.Format8bppIndexed); // Now lock the bitmap into memory using (Graphics g = Graphics.FromImage(copy)) { g.PageUnit = GraphicsUnit.Pixel; // Draw the source image onto the copy bitmap, // which will effect a widening as appropriate. g.DrawImage(source, bounds); } // Define a pointer to the bitmap data BitmapData sourceData = null; try { // Get the source image bits and lock into memory sourceData = copy.LockBits(bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb); // Call the FirstPass function if not a single pass algorithm. // For something like an octree quantizer, this will run through // all image pixels, build a data structure, and create a palette. if (!_singlePass) FirstPass(sourceData, width, height); // Then set the color palette on the output bitmap. I'm passing in the current palette // as there's no way to construct a new, empty palette. output.Palette = this.GetPalette(output.Palette); // Then call the second pass which actually does the conversion SecondPass(sourceData, output, width, height, bounds); } finally { // Ensure that the bits are unlocked copy.UnlockBits(sourceData); } // Last but not least, return the output bitmap return output; } /// <summary> /// Execute the first pass through the pixels in the image /// </summary> /// <param name="sourceData">The source data</param> /// <param name="width">The width in pixels of the image</param> /// <param name="height">The height in pixels of the image</param> protected virtual void FirstPass(BitmapData sourceData, int width, int height) { // Define the source data pointers. The source row is a byte to // keep addition of the stride value easier (as this is in bytes) byte* pSourceRow = (byte*)sourceData.Scan0.ToPointer(); Int32* pSourcePixel; // Loop through each row for (int row = 0; row < height; row++) { // Set the source pixel to the first pixel in this row pSourcePixel = (Int32*)pSourceRow; // And loop through each column for (int col = 0; col < width; col++, pSourcePixel++) // Now I have the pixel, call the FirstPassQuantize function... InitialQuantizePixel((Color32*)pSourcePixel); // Add the stride to the source row pSourceRow += sourceData.Stride; } } /// <summary> /// Execute a second pass through the bitmap /// </summary> /// <param name="sourceData">The source bitmap, locked into memory</param> /// <param name="output">The output bitmap</param> /// <param name="width">The width in pixels of the image</param> /// <param name="height">The height in pixels of the image</param> /// <param name="bounds">The bounding rectangle</param> protected virtual void SecondPass(BitmapData sourceData, Bitmap output, int width, int height, Rectangle bounds) { BitmapData outputData = null; try { // Lock the output bitmap into memory outputData = output.LockBits(bounds, ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed); // Define the source data pointers. The source row is a byte to // keep addition of the stride value easier (as this is in bytes) byte* pSourceRow = (byte*)sourceData.Scan0.ToPointer(); Int32* pSourcePixel = (Int32*)pSourceRow; Int32* pPreviousPixel = pSourcePixel; // Now define the destination data pointers byte* pDestinationRow = (byte*)outputData.Scan0.ToPointer(); byte* pDestinationPixel = pDestinationRow; // And convert the first pixel, so that I have values going into the loop byte pixelValue = QuantizePixel((Color32*)pSourcePixel); // Assign the value of the first pixel *pDestinationPixel = pixelValue; // Loop through each row for (int row = 0; row < height; row++) { // Set the source pixel to the first pixel in this row pSourcePixel = (Int32*)pSourceRow; // And set the destination pixel pointer to the first pixel in the row pDestinationPixel = pDestinationRow; // Loop through each pixel on this scan line for (int col = 0; col < width; col++, pSourcePixel++, pDestinationPixel++) { // Check if this is the same as the last pixel. If so use that value // rather than calculating it again. This is an inexpensive optimisation. if (*pPreviousPixel != *pSourcePixel) { // Quantize the pixel pixelValue = QuantizePixel((Color32*)pSourcePixel); // And setup the previous pointer pPreviousPixel = pSourcePixel; } // And set the pixel in the output *pDestinationPixel = pixelValue; } // Add the stride to the source row pSourceRow += sourceData.Stride; // And to the destination row pDestinationRow += outputData.Stride; } } finally { // Ensure that I unlock the output bits output.UnlockBits(outputData); } } /// <summary> /// Override this to process the pixel in the first pass of the algorithm /// </summary> /// <param name="pixel">The pixel to quantize</param> /// <remarks> /// This function need only be overridden if your quantize algorithm needs two passes, /// such as an Octree quantizer. /// </remarks> protected virtual void InitialQuantizePixel(Color32* pixel) { } /// <summary> /// Override this to process the pixel in the second pass of the algorithm /// </summary> /// <param name="pixel">The pixel to quantize</param> /// <returns>The quantized value</returns> protected abstract byte QuantizePixel(Color32* pixel); /// <summary> /// Retrieve the palette for the quantized image /// </summary> /// <param name="original">Any old palette, this is overrwritten</param> /// <returns>The new color palette</returns> protected abstract ColorPalette GetPalette(ColorPalette original); /// <summary> /// Flag used to indicate whether a single pass or two passes are needed for quantization. /// </summary> private bool _singlePass; /// <summary> /// Struct that defines a 32 bpp colour /// </summary> /// <remarks> /// This struct is used to read data from a 32 bits per pixel image /// in memory, and is ordered in this manner as this is the way that /// the data is layed out in memory /// </remarks> [StructLayout(LayoutKind.Explicit)] public struct Color32 { /// <summary> /// Holds the blue component of the colour /// </summary> [FieldOffset(0)] public byte Blue; /// <summary> /// Holds the green component of the colour /// </summary> [FieldOffset(1)] public byte Green; /// <summary> /// Holds the red component of the colour /// </summary> [FieldOffset(2)] public byte Red; /// <summary> /// Holds the alpha component of the colour /// </summary> [FieldOffset(3)] public byte Alpha; /// <summary> /// Permits the color32 to be treated as an int32 /// </summary> [FieldOffset(0)] public int ARGB; /// <summary> /// Return the color for this Color32 object /// </summary> public Color Color { get { return Color.FromArgb(Alpha, Red, Green, Blue); } } } } } </code></pre>

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