以下是一个简单的OpenGL ES马赛克处理的例子代码：
```c
#include <GLES2/gl2.h>
// 马赛克处理的像素数
#define MOSAIC_SIZE 10
// 顶点着色器代码
const char* vertexShaderCode =
"attribute vec4 a_Position;\n"
"void main() {\n"
" gl_Position = a_Position;\n"
"}\n";
// 片段着色器代码
const char* fragmentShaderCode =
"precision mediump float;\n"
"uniform sampler2D u_Texture;\n"
"uniform vec2 u_MosaicSize;\n"
"varying vec2 v_TexCoord;\n"
"void main() {\n"
" vec2 mosaicCoord = vec2(floor(v_TexCoord.x / u_MosaicSize.x), floor(v_TexCoord.y / u_MosaicSize.y));\n"
" vec2 mosaicTexCoord = vec2(mosaicCoord.x * u_MosaicSize.x, mosaicCoord.y * u_MosaicSize.y);\n"
" gl_FragColor = texture2D(u_Texture, mosaicTexCoord);\n"
"}\n";
// 顶点坐标数据
GLfloat vertices[] = {
-1.0f, 1.0f,
-1.0f, -1.0f,
1.0f, -1.0f,
1.0f, 1.0f,
};
// 纹理坐标数据
GLfloat texCoords[] = {
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f,
};
// 坐标索引数据
GLushort indices[] = {0, 1, 2, 0, 2, 3};
// 纹理ID
GLuint textureId;
// 着色器程序ID
GLuint programId;
void initTexture() {
// 创建纹理
glGenTextures(1, &textureId);
glBindTexture(GL_TEXTURE_2D, textureId);
// 设置纹理参数
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// 加载图片并设置纹理数据
int width, height, channels;
unsigned char* image = stbi_load("image.png", &width, &height, &channels, STBI_rgb_alpha);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image);
stbi_image_free(image);
}
void initShader() {
// 创建顶点着色器对象
GLuint vertexShaderId = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShaderId, 1, &vertexShaderCode, nullptr);
glCompileShader(vertexShaderId);
// 创建片段着色器对象
GLuint fragmentShaderId = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShaderId, 1, &fragmentShaderCode, nullptr);
glCompileShader(fragmentShaderId);
// 创建着色器程序对象
programId = glCreateProgram();
glAttachShader(programId, vertexShaderId);
glAttachShader(programId, fragmentShaderId);
glBindAttribLocation(programId, 0, "a_Position");
glBindAttribLocation(programId, 1, "a_TexCoord");
glLinkProgram(programId);
// 获取uniform变量的位置
GLint mosaicSizeLocation = glGetUniformLocation(programId, "u_MosaicSize");
// 设置uniform变量的值
glUniform2f(mosaicSizeLocation, MOSAIC_SIZE, MOSAIC_SIZE);
}
void initVertexBuffer() {
// 创建顶点缓冲区对象
GLuint vertexBufferId;
glGenBuffers(1, &vertexBufferId);
glBindBuffer(GL_ARRAY_BUFFER, vertexBufferId);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
// 创建纹理坐标缓冲区对象
GLuint texCoordBufferId;
glGenBuffers(1, &texCoordBufferId);
glBindBuffer(GL_ARRAY_BUFFER, texCoordBufferId);
glBufferData(GL_ARRAY_BUFFER, sizeof(texCoords), texCoords, GL_STATIC_DRAW);
// 创建索引缓冲区对象
GLuint indexBufferId;
glGenBuffers(1, &indexBufferId);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBufferId);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
// 设置顶点属性指针
GLuint positionLocation = glGetAttribLocation(programId, "a_Position");
glEnableVertexAttribArray(positionLocation);
glBindBuffer(GL_ARRAY_BUFFER, vertexBufferId);
glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, nullptr);
// 设置纹理坐标属性指针
GLuint texCoordLocation = glGetAttribLocation(programId, "a_TexCoord");
glEnableVertexAttribArray(texCoordLocation);
glBindBuffer(GL_ARRAY_BUFFER, texCoordBufferId);
glVertexAttribPointer(texCoordLocation, 2, GL_FLOAT, GL_FALSE, 0, nullptr);
}
void render() {
// 清空颜色缓冲区
glClear(GL_COLOR_BUFFER_BIT);
// 绑定纹理
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureId);
// 绘制矩形
glUseProgram(programId);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, nullptr);
}
int main() {
// 初始化OpenGL ES上下文
// 初始化纹理
initTexture();
// 初始化着色器程序
initShader();
// 初始化顶点缓冲区
initVertexBuffer();
// 渲染场景
render();
return 0;
}
```
在片段着色器中，我们使用了一个uniform变量`u_MosaicSize`来表示马赛克处理的像素数，计算出当前像素所在的马赛克块的坐标，然后再根据马赛克块的坐标计算出当前像素在马赛克块中的坐标，最后使用该坐标取纹理颜色，从而实现马赛克处理。在初始化着色器程序时，我们使用`glUniform2f`函数将`u_MosaicSize`的值设置为`MOSAIC_SIZE`。
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