#region License Information (GPL v3)
/*
ShareX - A program that allows you to take screenshots and share any file type
Copyright (C) 2007-2015 ShareX Developers
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
Optionally you can also view the license at .
*/
#endregion License Information (GPL v3)
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
namespace ShareX.HelpersLib
{
///
/// Summary description for Class1.
///
public abstract class Quantizer
{
///
/// Construct the quantizer
///
/// If true, the quantization only needs to loop through the source pixels once
///
/// 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'.
///
protected Quantizer(bool singlePass)
{
_singlePass = singlePass;
_pixelSize = Marshal.SizeOf(typeof(Color32));
}
///
/// Quantize an image and return the resulting output bitmap
///
/// The image to quantize
/// A quantized version of the image
public Bitmap Quantize(Image source)
{
// 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 = 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;
}
///
/// Execute the first pass through the pixels in the image
///
/// The source data
/// The width in pixels of the image
/// The height in pixels of the image
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)
IntPtr pSourceRow = sourceData.Scan0;
// Loop through each row
for (int row = 0; row < height; row++)
{
// Set the source pixel to the first pixel in this row
IntPtr pSourcePixel = pSourceRow;
// And loop through each column
for (int col = 0; col < width; col++)
{
InitialQuantizePixel(new Color32(pSourcePixel));
pSourcePixel = (IntPtr)((long)pSourcePixel + _pixelSize);
} // Now I have the pixel, call the FirstPassQuantize function...
// Add the stride to the source row
pSourceRow = (IntPtr)((long)pSourceRow + sourceData.Stride);
}
}
///
/// Execute a second pass through the bitmap
///
/// The source bitmap, locked into memory
/// The output bitmap
/// The width in pixels of the image
/// The height in pixels of the image
/// The bounding rectangle
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)
IntPtr pSourceRow = sourceData.Scan0;
IntPtr pSourcePixel = pSourceRow;
IntPtr pPreviousPixel = pSourcePixel;
// Now define the destination data pointers
IntPtr pDestinationRow = outputData.Scan0;
IntPtr pDestinationPixel = pDestinationRow;
// And convert the first pixel, so that I have values going into the loop
byte pixelValue = QuantizePixel(new Color32(pSourcePixel));
// Assign the value of the first pixel
Marshal.WriteByte(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 = 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++)
{
// 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 (Marshal.ReadInt32(pPreviousPixel) != Marshal.ReadInt32(pSourcePixel))
{
// Quantize the pixel
pixelValue = QuantizePixel(new Color32(pSourcePixel));
// And setup the previous pointer
pPreviousPixel = pSourcePixel;
}
// And set the pixel in the output
Marshal.WriteByte(pDestinationPixel, pixelValue);
pSourcePixel = (IntPtr)((long)pSourcePixel + _pixelSize);
pDestinationPixel = (IntPtr)((long)pDestinationPixel + 1);
}
// Add the stride to the source row
pSourceRow = (IntPtr)((long)pSourceRow + sourceData.Stride);
// And to the destination row
pDestinationRow = (IntPtr)((long)pDestinationRow + outputData.Stride);
}
}
finally
{
// Ensure that I unlock the output bits
output.UnlockBits(outputData);
}
}
///
/// Override this to process the pixel in the first pass of the algorithm
///
/// The pixel to quantize
///
/// This function need only be overridden if your quantize algorithm needs two passes,
/// such as an Octree quantizer.
///
protected virtual void InitialQuantizePixel(Color32 pixel)
{
}
///
/// Override this to process the pixel in the second pass of the algorithm
///
/// The pixel to quantize
/// The quantized value
protected abstract byte QuantizePixel(Color32 pixel);
///
/// Retrieve the palette for the quantized image
///
/// Any old palette, this is overrwritten
/// The new color palette
protected abstract ColorPalette GetPalette(ColorPalette original);
///
/// Flag used to indicate whether a single pass or two passes are needed for quantization.
///
private bool _singlePass;
private int _pixelSize;
///
/// Struct that defines a 32 bpp colour
///
///
/// 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
///
[StructLayout(LayoutKind.Explicit)]
public struct Color32
{
public Color32(IntPtr pSourcePixel)
{
this = (Color32)Marshal.PtrToStructure(pSourcePixel, typeof(Color32));
}
///
/// Holds the blue component of the colour
///
[FieldOffset(0)]
public byte Blue;
///
/// Holds the green component of the colour
///
[FieldOffset(1)]
public byte Green;
///
/// Holds the red component of the colour
///
[FieldOffset(2)]
public byte Red;
///
/// Holds the alpha component of the colour
///
[FieldOffset(3)]
public byte Alpha;
///
/// Permits the color32 to be treated as an int32
///
[FieldOffset(0)]
public int ARGB;
///
/// Return the color for this Color32 object
///
public Color Color
{
get
{
return Color.FromArgb(Alpha, Red, Green, Blue);
}
}
}
}
}