Question

我正在为iPhone和iPad开发绘画应用程序[参考GLPaint应用程序]。我正在研究画笔效果。我想为我的绘画应用程序获得画笔效果，如Image1

所示

enter image description here

我的画笔笔触类似于图像2

enter image description here

我正在使用以下代码进行画笔纹理：

CGImageRef      brushImage;
CGContextRef    brushContext;
GLubyte         *brushData;
size_t          width, height;
    if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
    {
        brushImage = [UIImage imageNamed:@"flower@2x.png"].CGImage;
    }
    else {
        brushImage = [UIImage imageNamed:@"flower.png"].CGImage;
    }
    width = CGImageGetWidth(brushImage)   ;
    height = CGImageGetHeight(brushImage) ;
    if(brushImage) {

        brushData = (GLubyte *) calloc(width * height * 4, sizeof(GLubyte));
                brushContext = CGBitmapContextCreate(brushData, width, height, 8, width * 4, CGImageGetColorSpace(brushImage),kCGImageAlphaPremultipliedLast);
        CGContextDrawImage(brushContext, CGRectMake(0.0, 0.0, (CGFloat)width, (CGFloat)height), brushImage);
        CGContextRelease(brushContext);
        glGenTextures(1, &brushTexture);
        glBindTexture(GL_TEXTURE_2D, brushTexture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, brushData);
        free(brushData);
    }
        CGFloat scale;
        scale = self.contentScaleFactor;

    glMatrixMode(GL_PROJECTION);
    CGRect frame = self.bounds;
    glLoadIdentity();
    glOrthof(0, (frame.size.width) * scale, 0, (frame.size.height) * scale, -1, 1);
    glViewport(0, 0, (frame.size.width) * scale, (frame.size.height) * scale);
    glMatrixMode(GL_MODELVIEW);
    glDisable(GL_DITHER);
    glEnable(GL_BLEND);
    glEnable(GL_TEXTURE_2D);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_POINT_SPRITE_OES);
    glTexEnvf(GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE);
    glPointSize(width / kBrushScale);
    // Define a starting color 
    HSL2RGB((CGFloat) 0.0 / (CGFloat)kPaletteSize, kSaturation, kLuminosity, &components[0], &components[1], &components[2]);
    glColor4f(components[0] * kBrushOpacity, components[1] * kBrushOpacity, components[2] * kBrushOpacity, kBrushOpacity);

我一直在寻找与不同画笔笔划相关的代码，但我找不到任何代码。帮助我获得类似于image1的“所需”笔刷笔触。

Answer 1

请勿使用GL_POINT_SPRITE_OES模式。通过标准三角形绘制精灵。然后它需要将精灵纹理坐标绑定到目标输出坐标并使精灵纹理可重复。假设精灵纹理大小为32x32。默认纹理坐标位于rect {{0,0},{1.0,1.0}}中。要在{x,y}位置绘制精灵，需要使用基于rect {{(x%32)/32.0, (y%32)/32.0},{1.0, 1.0}}的精灵纹理坐标。这样可以防止精灵内容弄脏。

iPhone OpenGL ES Paint App刷效果

1 个答案: