OpenGL ES画板
Posted lybskill
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一、概述
利用自定义顶点和片元着色器渲染,并且设置图片纹理颜色为画笔颜色
二、核心代码
- (void)renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end { //顶点缓存区 static GLfloat *vertexBuffer = NULL; //顶点Max static NSUInteger vertexMax = 64; //顶点个数 NSUInteger vertexCount = 0,count; CGFloat scale = self.contentScaleFactor; //点到像素转换:乘以比例因子 start.x *= scale; start.y *= scale; end.x *= scale; end.y *= scale; //开辟顶点缓存区 if (vertexBuffer == NULL) { vertexBuffer = malloc(vertexMax*2*sizeof(GLfloat)); } //求得两点之间的距离 float seq = sqrtf((end.x-start.x)*(end.x-start.x)+(end.y-start.y)*(end.y-start.y)); /*向上取整:求得距离要产生多少个点 kBrushPixelStep值越大,笔触越细;值越小,笔触越粗 */ NSInteger pointCount = ceil(seq/kBrushPixelStep); count = MAX(pointCount, 1); for (int i = 0; i < count; i++) { if (vertexCount == vertexMax) { //修改2倍增长 vertexMax = 2*vertexMax; vertexBuffer = realloc(vertexBuffer, vertexMax*2*sizeof(GLfloat)); } //计算两个之间的距离有多少个点,并存储在顶点缓存区中 vertexBuffer[2*vertexCount+0] = start.x+(end.x-start.x)*((GLfloat)i/(GLfloat)count); vertexBuffer[2*vertexCount+1] = start.y+(end.y-start.y)*((GLfloat)i/(GLfloat)count); vertexCount++; } //绑定顶点数据 glBindBuffer(GL_ARRAY_BUFFER, vboID); //将数据从CPU中复制到GPU中提供给OpenGL使用 glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vertexBuffer, GL_DYNAMIC_DRAW); //启用指定属性 glEnableVertexAttribArray(ATTRIB_VERTEX); //链接顶点属性 glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 2*sizeof(GLfloat), 0); //使用数据总线:传递顶点数据到顶点着色器 glUseProgram(program[PROGRAME_POINT].id); //绘制顶点:绘制模型、起始点、顶点个数 glDrawArrays(GL_POINTS, 0, (int)vertexCount); //绑定渲染缓存区到特定标志符上 glBindRenderbuffer(GL_RENDERBUFFER, viewRenderBuffer); //开始渲染 [context presentRenderbuffer:GL_RENDERBUFFER]; }
- (textureInfo_t)textureFromName:(NSString *)name { CGImageRef brushImage; CGContextRef brushContext; GLubyte *brushData; size_t width, height; GLuint texID; textureInfo_t texture; brushImage = [UIImage imageNamed:name].CGImage; width = CGImageGetWidth(brushImage); height = CGImageGetHeight(brushImage); //开辟纹理图片内存 brushData = (GLubyte *)calloc(width*height*4, sizeof(GLubyte)); /*创建位图上下文 参数:图片内存地址、图片宽、图片高、像素组件位数(一般设置8),每一行所占比特数、颜色空间、颜色通道 */ brushContext = CGBitmapContextCreate(brushData, width, height, 8, width*4, CGImageGetColorSpace(brushImage), kCGImageAlphaPremultipliedLast); //绘图 CGContextDrawImage(brushContext, CGRectMake(0, 0, (CGFloat)width, (CGFloat)height), brushImage); //释放上下文 CGContextRelease(brushContext); //申请纹理标志符 glGenTextures(1, &texID); //绑定纹理 glBindTexture(GL_TEXTURE_2D, texID); //设置纹理属性:缩小滤波器、线性滤波器 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); /*生成2D纹理图片 参数:纹理目标、图像级别(0为基本级别)、颜色组件(GL_RGBA、GL_ALPHA)、图像宽、图像高、边框宽度(一般为0)、像素数据颜色格式、像素数据类型、内存中指向图像数据指针 */ glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (int)width, (int)height, 0, GL_RGBA, GL_UNSIGNED_BYTE, brushData); free(brushData); //配置纹理属性 texture.id = texID; texture.width = (int)width; texture.height = (int)height; return texture; }
- (void)setupShaders { for (int i = 0; i < NUM_PROGRAMS; i++) { //读取顶点着色器程序 char *vsrc = readFile(pathForResource(program[i].vert)); //读取片元着色器程序 char *fsrc = readFile(pathForResource(program[i].frag)); NSString *vsrcStr = [[NSString alloc] initWithBytes:vsrc length:strlen(vsrc)-1 encoding:NSUTF8StringEncoding]; NSString *fsrcStr = [[NSString alloc] initWithBytes:fsrc length:strlen(fsrc)-1 encoding:NSUTF8StringEncoding]; NSLog(@"vsrcStr------%@", vsrcStr); NSLog(@"fsrcStr------%@", fsrcStr); GLsizei attribCt = 0; GLchar *attribUsed[NUM_ATTRIBS]; GLint attrib[NUM_ATTRIBS]; GLchar *attribName[NUM_ATTRIBS] = { "inVertex" }; const char *uniformName[NUM_UNIFORMS] = { "MVP","pointSize","vertexColor", "texture" }; for (int j = 0; j < NUM_ATTRIBS; j++) { if (strstr(vsrc, attribName[j])) { attrib[attribCt] = j; attribUsed[attribCt++] = attribName[j]; } } //program处理:创建、链接、生成 glueCreateProgram(vsrc, fsrc, attribCt, (const char **)&attribUsed[0], attrib, NUM_UNIFORMS, &uniformName[0], program[i].uniform, &program[i].id); free(vsrc); free(fsrc); if (i == PROGRAME_POINT) { glUseProgram(program[PROGRAME_POINT].id); //为当前程序指定uniform变量 glUniform1i(program[PROGRAME_POINT].uniform[UNIFORM_TEXTURE], 0); //设置正射投影矩阵 GLKMatrix4 projectionMatrix = GLKMatrix4MakeOrtho(0, backingWidth, 0, backingHeight, -1, 1); //创建模型视图矩阵:单元矩阵 GLKMatrix4 modelViewMatrix = GLKMatrix4Identity; //正射投影矩阵与模型视图矩阵相乘,结果保存在MVPMatrix矩阵中 GLKMatrix4 MVPMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix); /*为当前程序指定Uniform变量值 参数:指明要更改的Uniform变量的位置、将要被修改的矩阵的数量、矩阵值被载入变量时是否要对举证进行变换(如转置)、将要用于更新uniform变量MVP的数组指针 */ glUniformMatrix4fv(program[PROGRAME_POINT].uniform[UNIFORM_MVP], 1, GL_FALSE, MVPMatrix.m); //为当前程序对象Uniform变量的pointSize赋值 glUniform1f(program[PROGRAME_POINT].uniform[UNIFORM_POINT_SIZE], brushTexture.width/kBrushScale); //为当前程序对象Uniform变量顶点颜色赋值 glUniform4fv(program[PROGRAME_POINT].uniform[UNIFORM_VERTEX_COLOR], 1, brushColor); } } glError(); }
三、效果图
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