cocos2d-iphone - cocos2d 大纲

Question

如何在 cocos2d 中为基于 alpha 的纹理绘制轮廓？我有一个纹理，我想在 alpha 从 0 到非零交叉的任何地方画一条线，这样它就可以勾勒出所有东西。

Answer 1

我自己通过将图像复制到内存然后使用它来解决它:
我使用了渲染纹理，但如果您不想使用，我添加了有关更改内容的注释

    // Get the size of the render texture, change to size of screen if you don't
    // use render texture
    CGSize s = RenderedWall.sprite.texture.contentSizeInPixels;
    int tx = s.width;
    int ty = s.height;

    int bitsPerComponent            = 8;
    int bytesPerPixel               = (bitsPerComponent * 4)/8;
    int bytesPerRow                 = bytesPerPixel * tx;
    NSInteger myDataLength          = bytesPerRow * ty;

    NSMutableData *buffer = [[NSMutableData alloc] initWithCapacity:myDataLength];
    Byte *bytes = (Byte *)[buffer mutableBytes];

    glReadPixels(0, 0, tx, ty, GL_RGBA, GL_UNSIGNED_BYTE, bytes);

    NSMutableData *newBuffer = [[NSMutableData alloc] initWithBytes:bytes length:myDataLength];
    Byte *newBytes = (Byte *)[newBuffer mutableBytes];

    // free the render texture, remove this if you don't use one
    [RenderedWall end];

    for(int x = 0; x < tx; x++)
    {
        for(int y = 0; y < ty; y++)
        {
            int idx = y * bytesPerRow + x * bytesPerPixel + 3;

            int w = 1;

            if(bytes[idx] <= 254)
            {
                bool ok = false;
                for(int nx = -w; nx <= w; nx++)
                {
                    for(int ny = -w; ny <= w; ny++)
                    {
                        if(x + nx < 0 || y + ny < 0 || x + nx >= tx || y + ny >= ty)
                            continue;
                        if(bytes[idx + nx * bytesPerPixel + ny * bytesPerRow] == 255)
                        {
                            ok = true;
                            break;
                        }
                    }
                }
                if(ok)
                {
                    newBytes[idx - 3] = 0;
                    newBytes[idx - 2] = 0;
                    newBytes[idx - 1] = 0;
                    newBytes[idx] = 255;
                }
            }
        }
    }

    CCTexture2D *texture = [[CCTexture2D alloc] initWithData:newBytes
                                                 pixelFormat:kCCTexture2DPixelFormat_RGBA8888
                                                  pixelsWide:tx pixelsHigh:ty
                                                 contentSize:RenderedWall.sprite.texture.contentSize];

    // The outlined sprite comes here. If you don't use render texture, you need to add clear here.

    CCSprite *RenderedWallSprite = [CCSprite spriteWithTexture:texture];