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在意識到沒有MonoTouch的實時圖形效果庫之後，我決定編寫我自己的。經過一番研究後，我寫了一個完美的卷積方法，但即使使用不安全的代碼，其速度也非常慢。 我做錯了什麼？是否有一些我錯過的優化？如何在MonoTouch中優化此圖像卷積濾鏡方法？
這裏是我的c＃類，任何建議，不管多小，都歡迎！
using System;
using System.Drawing;
using MonoTouch.CoreGraphics;
using System.Runtime.InteropServices;
using MonoTouch.UIKit;
using MonoTouch;
namespace FilterLibrary
{
public class ConvMatrix
{
public int Factor { get; set; }
public int Offset { get; set; }
private int[,] _matrix = { {0, 0, 0, 0, 0},
{0, 0, 0, 0, 0},
{0, 0, 1, 0, 0},
{0, 0, 0, 0, 0},
{0, 0, 0, 0, 0}
};
public int[,] Matrix
{
get { return _matrix; }
set
{
_matrix = value;
Factor = 0;
for (int i = 0; i < Size; i++)
for (int j = 0; j < Size; j++)
Factor += _matrix[i, j];
if (Factor == 0)
Factor = 1;
}
}
private int _size = 5;
public int Size
{
get { return _size; }
set
{
if (value != 1 && value != 3 && value != 5 && value != 7)
_size = 5;
else
_size = value;
}
}
public ConvMatrix()
{
Offset = 0;
Factor = 1;
}
}
public class ConvolutionFilter
{
public ConvolutionFilter()
{
}
public static CGImage GaussianSmooth (CGImage image)
{
ConvMatrix matr = new ConvMatrix();
matr.Matrix = new int[5, 5] {
{ 1 , 4 , 7 , 4 , 1 },
{ 4 ,16 ,26 ,16 , 4 },
{ 7 ,26 ,41 ,26 , 7 },
{ 4 ,16 ,26 ,16 , 4 },
{ 1 , 4 , 7 , 4 , 1 }
};
return Filter.ImageConvolution (image, matr);
}
public static CGImage MotionBlur (CGImage image)
{
ConvMatrix matr = new ConvMatrix();
matr.Size = 7;
matr.Matrix = new int[7, 7] {
{ 1 , 0 , 0 , 0 , 0 , 0 , 0},
{ 0 , 1 , 0 , 0 , 0 , 0 , 0},
{ 0 , 0 , 1 , 0 , 0 , 0 , 0},
{ 0 , 0 , 0 , 1 , 0 , 0 , 0},
{ 0 , 0 , 0 , 0 , 1 , 0 , 0},
{ 0 , 0 , 0 , 0 , 0 , 1 , 0},
{ 0 , 0 , 0 , 0 , 0 , 0 , 1}
};
return Filter.ImageConvolution (image, matr);
}
public static CGBitmapContext ConvertToBitmapRGBA8 (CGImage imageRef)
{
// Create an empty bitmap context to draw the uiimage into
CGBitmapContext context = NewEmptyBitmapRGBA8ContextFromImage (imageRef);
if (context == null) {
Console.WriteLine ("ERROR: failed to create bitmap context");
return null;
}
RectangleF rect = new RectangleF (0.0f, 0.0f, imageRef.Width, imageRef.Height);
context.ClearRect (rect); //Clear memory area from old garbage
context.DrawImage (rect, imageRef); // Draw image into the context to get the raw image data in our format
return context;
}
public static CGBitmapContext NewEmptyBitmapRGBA8ContextFromImage (CGImage image)
{
CGBitmapContext context = null;
CGColorSpace colorSpace;
IntPtr bitmapData;
int bitsPerComponent = 8; //Forcing only 8 bit formats for now...
int width = image.Width;
int height = image.Height;
int bytesPerRow = image.BytesPerRow;
int bufferLength = bytesPerRow * height;
colorSpace = CGColorSpace.CreateDeviceRGB();
if (colorSpace == null) {
Console.WriteLine ("Error allocating color space RGB");
return null;
}
// Allocate memory for image data
bitmapData = Marshal.AllocHGlobal (bufferLength);
//Create bitmap context forcing Premultiplied Alpha as required by Apple iOS
if (image.AlphaInfo == CGImageAlphaInfo.PremultipliedFirst || image.AlphaInfo == CGImageAlphaInfo.First) {
context = new CGBitmapContext (bitmapData,
width,
height,
bitsPerComponent,
bytesPerRow,
colorSpace,
CGImageAlphaInfo.PremultipliedFirst); // ARGB
} else {
if (image.AlphaInfo == CGImageAlphaInfo.PremultipliedLast || image.AlphaInfo == CGImageAlphaInfo.Last) {
context = new CGBitmapContext (bitmapData,
width,
height,
bitsPerComponent,
bytesPerRow,
colorSpace,
CGImageAlphaInfo.PremultipliedLast); //RGBA
} else {
Console.WriteLine ("ERROR image format non supported: " + image.AlphaInfo);
throw new Exception ("ERROR image format non supported: " + image.AlphaInfo);
}
}
if (context == null) {
Console.WriteLine ("Bitmap context from BitmapData not created");
}
return context;
}
public static CGImage ImageConvolution (CGImage image, ConvMatrix fmat)
{
//Avoid division by 0
if (fmat.Factor == 0)
return image;
//Create a clone of the original image
CGImage srcImage = image.Clone();
//init some temporary vars
int x, y, filterx, filtery, tempx, tempy;
int s = fmat.Size/2;
int a, r, g, b, tr, tg, tb, ta;
int a_div;
float a_mul;
//Compute pixel size (bytes per pixel)
int pixelSize = image.BitsPerPixel/image.BitsPerComponent;
//Create bitmap contexts
CGBitmapContext imageData = ConvertToBitmapRGBA8 (image);
CGBitmapContext srcImageData = ConvertToBitmapRGBA8 (srcImage);
// Scan0 is the memory address where pixel-array begins.
IntPtr scan0 = srcImageData.Data;
// Stride is the width of each row of pixels.
int stride = srcImageData.BytesPerRow;
unsafe {
byte* tempPixel;
for (y = s; y < srcImageData.Height - s; y++) {
for (x = s; x < srcImageData.Width - s; x++) {
a = r = g = b = 0;
a_div = 0;
a_mul = 0.0f;
//Convolution
for (filtery = 0; filtery < fmat.Size; filtery++) {
for (filterx = 0; filterx < fmat.Size; filterx++) {
// Get nearby pixel's position
tempx = x + filterx - s;
tempy = y + filtery - s;
// Go to that pixel in pixel-array
tempPixel = (byte*)scan0 + (tempy * stride) + (tempx * pixelSize);
if (srcImageData.AlphaInfo == CGImageAlphaInfo.First) {
// The format is ARGB (1 byte each).
ta = (int)*tempPixel;
tr = (int)*(tempPixel + 1);
tg = (int)*(tempPixel + 2);
tb = (int)*(tempPixel + 3);
a += fmat.Matrix [filtery, filterx] * ta;
r += fmat.Matrix [filtery, filterx] * (tr);
g += fmat.Matrix [filtery, filterx] * (tg);
b += fmat.Matrix [filtery, filterx] * (tb);
}
if (srcImageData.AlphaInfo == CGImageAlphaInfo.Last) {
// The format is RGBA (1 byte each).
tr = (int)*tempPixel;
tg = (int)*(tempPixel + 1);
tb = (int)*(tempPixel + 2);
ta = (int)*(tempPixel + 3);
a += fmat.Matrix [filtery, filterx] * ta;
r += fmat.Matrix [filtery, filterx] * (tr);
g += fmat.Matrix [filtery, filterx] * (tg);
b += fmat.Matrix [filtery, filterx] * (tb);
}
if (srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedFirst) {
// The format is premultiplied ARGB (1 byte each).
ta = (int)*tempPixel;
tr = (int)*(tempPixel + 1);
tg = (int)*(tempPixel + 2);
tb = (int)*(tempPixel + 3);
// Computing alpha
a += fmat.Matrix [filtery, filterx] * ta;
a_div = (ta/255);
// Computing rgb
if (a_div == 0) {
r += fmat.Matrix [filtery, filterx] * (tr);
g += fmat.Matrix [filtery, filterx] * (tg);
b += fmat.Matrix [filtery, filterx] * (tb);
} else {
r += fmat.Matrix [filtery, filterx] * (tr/a_div); // "Dividing the premultiplied value by the
g += fmat.Matrix [filtery, filterx] * (tg/a_div); // alpha value to get the original color
b += fmat.Matrix [filtery, filterx] * (tb/a_div); // value before matrix multiplication"
}
}
if (srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedLast) {
// The format is premultiplied RGBA (1 byte each). Get em
tr = (int)*tempPixel;
tg = (int)*(tempPixel + 1);
tb = (int)*(tempPixel + 2);
ta = (int)*(tempPixel + 3);
// Computing alpha
a += fmat.Matrix [filtery, filterx] * ta;
a_div = (ta/255);
// Computing rgb
if (a_div == 0) {
r += fmat.Matrix [filtery, filterx] * (tr);
g += fmat.Matrix [filtery, filterx] * (tg);
b += fmat.Matrix [filtery, filterx] * (tb);
} else {
r += fmat.Matrix [filtery, filterx] * (tr/a_div); // "Dividing the premultiplied value by the
g += fmat.Matrix [filtery, filterx] * (tg/a_div); // alpha value to get the original color
b += fmat.Matrix [filtery, filterx] * (tb/a_div); // value before matrix multiplication"
}
}
}
}
// Remove values out of [0,255]
a = Math.Min (Math.Max ((a/fmat.Factor) + fmat.Offset, 0), 255);
r = Math.Min (Math.Max ((r/fmat.Factor) + fmat.Offset, 0), 255);
g = Math.Min (Math.Max ((g/fmat.Factor) + fmat.Offset, 0), 255);
b = Math.Min (Math.Max ((b/fmat.Factor) + fmat.Offset, 0), 255);
// Premultiplying color value by alpha value if needed by image format
if (srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedFirst || srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedLast) {
a_mul = (a/255.0f);
r = (int)(r * a_mul);
g = (int)(g * a_mul);
b = (int)(b * a_mul);
}
// Finally compute new pixel position (in new image) and write the pixels.
if (srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedFirst || srcImageData.AlphaInfo == CGImageAlphaInfo.First) {
// The format is ARGB (1 byte each)
byte* newpixel = (byte*)imageData.Data + (y * imageData.BytesPerRow) + (x * pixelSize);
*newpixel = (byte)a;
*(newpixel + 1) = (byte)r;
*(newpixel + 2) = (byte)g;
*(newpixel + 3) = (byte)b;
}
if (srcImageData.AlphaInfo == CGImageAlphaInfo.PremultipliedLast || srcImageData.AlphaInfo == CGImageAlphaInfo.Last) {
// The format is RGBA (1 byte each)
byte* newpixel = (byte*)imageData.Data + (y * imageData.BytesPerRow) + (x * pixelSize);
*newpixel = (byte)r;
*(newpixel + 1) = (byte)g;
*(newpixel + 2) = (byte)b;
*(newpixel + 3) = (byte)a;
}
}
}
}
return imageData.ToImage();
}
}
}
感謝您的回答。不幸的是，Core Image僅在iOS 5.0上可用，而MonoTouch目前還不支持。 :(我會嘗試從循環中移除這些ifs –
MonoTouch 4.9.x支持iOS5 beta 7，我們希望本週發佈MonoTouch 5.0版本，就在Apple發佈後 – jstedfast
謝謝！好消息！ –