iphone - 在 Paint Application 中撤消绘图

Question

我正在使用 OpenGl 框架制作一个绘画应用程序，但我卡在了 UNDO/REDO 选项。我实现的代码是这样的:

  -(void)undo_called
{

artbrushAppDelegate *app=(artbrushAppDelegate *)[[UIApplication sharedApplication]delegate];
mbrushscale=app.brushscale;
brushimage=app.brush_image;
Erase=YES;
[self playRayundo];
 }


-(void)playRayundo
{
artbrushAppDelegate *app=(artbrushAppDelegate *)[[UIApplication sharedApplication]delegate];
glColor4f(app.r1g,
          app.b1g,
          app.g1g,
          0);
NSLog(@"%f",app.r1g);


if(undo != NULL)
{
    for(int l = 0; l < [undo count]; l++)
    {
        //replays my writRay -1 because of location point
        for(int p = 0; p < [[undo objectAtIndex:l]count]-1; p ++)
        {
            [self drawErase:[[[undo objectAtIndex:l]objectAtIndex:p]CGPointValue] toPoint:[[[undo objectAtIndex:l]objectAtIndex:p + 1]CGPointValue]];
        }
    }
}

Erase=NO;
glColor4f(app.rg,
          app.bg,
          app.gg,
          kBrushOpacity);

  }



 -(void) drawErase:(CGPoint)start toPoint:(CGPoint)end

 {
    static GLfloat*     eraseBuffer = NULL;
    static NSUInteger   eraseMax = 64;

NSUInteger          vertexCount = 0,
count,
i;

[EAGLContext setCurrentContext:context];
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);

// Convert locations from Points to Pixels
CGFloat scale = 1.0;//self.contentScaleFactor;
start.x *= scale;
start.y *= scale;
end.x *= scale;
end.y *= scale;

// Allocate vertex array buffer
if(eraseBuffer == NULL)
    eraseBuffer = malloc(eraseMax * 2 * sizeof(GLfloat));

// Add points to the buffer so there are drawing points every X pixels      
count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y - start.y) * (end.y - start.y)) / kBrushPixelStep), 1);

for(i = 0; i < count; ++i) 
{
    if(vertexCount == eraseMax) 
    {
        eraseMax = 2 * eraseMax;
        eraseBuffer = realloc(eraseBuffer, eraseMax * 2 * sizeof(GLfloat));
    }

    eraseBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i / (GLfloat)count);
    eraseBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i / (GLfloat)count);
    vertexCount += 1;
  }

  [self ChangebrushPic:brushimage];

 //the erase brush color  is transparent.

glEnable(GL_POINT_SPRITE_OES);
glTexEnvf(GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE);
glPointSize(64/mbrushscale);

// Render the vertex array

glVertexPointer(2, GL_FLOAT, 0, eraseBuffer);
glDrawArrays(GL_POINTS, 0, vertexCount);


// Display the buffer
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];

// at last restore the  mixed-mode
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

 }

这段代码效率不高，而且有很多错误。看看撤消前后的图像。

之前:http://imageshack.us/photo/my-images/577/screenshot20110714at121.png/

之后:http://imageshack.us/photo/my-images/200/screenshot20110714at121.png/

所以我想在每次用户的 Touch 结束时将图像保存在缓冲区中并在 UNDO 上调用之前的图像..任何人都可以帮助我如何将图像存储在缓冲区中并在 UNDO 上取回？我试图找到它的示例代码，但找不到..

谢谢..

Answer 1

好的。我发布了我自己的问题的答案，因为似乎有很多人提到这个问题。

有一个名为TouchPainter 的应用程序及其source code可用。它包含绘图、颜色混合、撤消/重做(惊人的..!!)、保存/打开绘图..

注意:它可能需要非常深入的Objective C和设计模式知识(我仍然不知道什么是设计模式。但我找到了它，所以我正在分享..)。整个应用程序的源代码在“Apress.Pro Objective-C Design Patterns for iOS”这本书中进行了解释。

希望对您有所帮助..:)祝您好运..