参看资料：
https://juejin.im/post/5cfa680b6fb9a07ef63fced8
OpenGL加载纹理
//
// ViewController.m
// openGL-加载图片
//
// Created by mac on 2020/2/25.
// Copyright © 2020 cc. All rights reserved.
//
#import "ViewController.h"
#import <GLKit/GLKit.h>
typedef struct {
GLKVector3 positionCoord;
GLKVector2 textureCoord;
} SenceVertex;
@interface ViewController ()
@property (nonatomic,strong) UIImageView *imageView;
@property (nonatomic, assign) SenceVertex *vertices;
@property (nonatomic, strong) EAGLContext *context;
@property (nonatomic, strong) CAEAGLLayer* myLayer;
// 用于刷新屏幕
@property (nonatomic, strong) CADisplayLink *displayLink;
// 开始的时间戳
@property (nonatomic, assign) NSTimeInterval startTimeInterval;
// 着色器程序
@property (nonatomic, assign) GLuint program;
// 顶点缓存
@property (nonatomic, assign) GLuint vertexBuffer;
// 纹理 ID
@property (nonatomic, assign) GLuint textureID;
@end
@implementation ViewController
-(void)viewDidLoad{
[self initFilter];
}
- (void)initFilter{
[self setupCoord];
[self setupContext];
[self setupLayer];
[self bindRenderLayer:self.myLayer];
[self bindImage:[[NSBundle mainBundle] pathForResource:@"image01.jpg" ofType:nil]];
[self setupPort];
[self bindTopBuffer];
[self setupShaderProgramWidthName:@"Normal"];
[self startTimer];
}
- (void)removeTimer{
if (self.displayLink) {
[self.displayLink invalidate];
self.displayLink = nil;
}
}
- (void)startTimer{
[self removeTimer];
self.startTimeInterval = 0;
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(timeAction)];
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
}
- (void)timeAction {
//DisplayLink 的当前时间撮
if (self.startTimeInterval == 0) {
self.startTimeInterval = self.displayLink.timestamp;
}
//使用program
glUseProgram(self.program);
//绑定buffer
glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer);
// 传入时间
CGFloat currentTime = self.displayLink.timestamp - self.startTimeInterval;
GLuint time = glGetUniformLocation(self.program, "Time");
glUniform1f(time, currentTime);
// 清除画布
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(1, 1, 1, 1);
// 重绘
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
//渲染到屏幕上
[self.context presentRenderbuffer:GL_RENDERBUFFER];
[self imageFromTextureWithWidth:[self drawableWidth] height:[self drawableHeight]];
}
//渲染上下文
- (void)setupContext{
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
if (!self.context) {
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
}
[EAGLContext setCurrentContext:self.context];
}
//设置图层(CAEAGLLayer)
- (void)setupLayer{
self.myLayer = [[CAEAGLLayer alloc] init];
self.myLayer.frame = CGRectMake(0, 50, self.view.frame.size.width, self.view.frame.size.width);
self.myLayer.contentsScale = [UIScreen mainScreen].scale;
self.myLayer.opaque = NO; //CALayer默认是透明的，透明的对性能负荷大，故将其关闭
self.myLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
// 由应用层来进行内存管理
@(NO),kEAGLDrawablePropertyRetainedBacking,
kEAGLColorFormatRGBA8,kEAGLDrawablePropertyColorFormat,
nil];
[self.view.layer addSublayer:self.myLayer];
}
//绑定渲染缓冲区
- (void)bindRenderLayer:(CAEAGLLayer*)layer{
// 渲染缓冲区、帧缓冲区对象
GLuint renderBuffer;
GLuint frameBuffer;
// 获取渲染缓冲区，绑定渲染缓存区以及将渲染缓冲区与layer建立连接
glGenRenderbuffers(1, &renderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
[self.context renderbufferStorage:GL_RENDERBUFFER fromDrawable:layer];
// 获取帧缓冲区名称， 绑定帧缓冲区以及将渲染缓冲区附着到帧缓冲区上
glGenFramebuffers(1, &frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderBuffer);
}
//设置顶点缓冲区
- (void)bindTopBuffer{
// 设置顶点缓存区
GLuint vertexBuffer;
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
GLsizeiptr bufferSizeBytes = sizeof(SenceVertex) * 4;
glBufferData(GL_ARRAY_BUFFER, bufferSizeBytes, self.vertices, GL_DYNAMIC_DRAW);
self.vertexBuffer = vertexBuffer;
}
//初始化坐标
- (void)setupCoord{
// 开辟顶点数组内存空间
self.vertices = malloc(sizeof(SenceVertex) * 4);
// 初始化顶点数据以及纹理坐标
self.vertices[0] = (SenceVertex){{-1, 1, 0}, {0, 1}};
self.vertices[1] = (SenceVertex){{-1, -1, 0}, {0, 0}};
self.vertices[2] = (SenceVertex){{1, 1, 0}, {1, 1}};
self.vertices[3] = (SenceVertex){{1, -1, 0}, {1, 0}};
}
//读取图片+设置纹理ID
- (void)bindImage:(NSString*)imagePath{
// 读取图片
UIImage *image = [UIImage imageWithContentsOfFile:imagePath];
// 将图片转换成纹理图片
GLuint textureID = [self createTextureWithImage:image];
// 设置纹理ID
self.textureID = textureID;
}
// 设置视口
- (void)setupPort{
glViewport(0, 0, self.drawableWidth, self.drawableHeight);
}
// 从图片中加载纹理
- (GLuint)createTextureWithImage:(UIImage *)image {
CGImageRef cgImageRef = [image CGImage];
GLuint width = (GLuint)CGImageGetWidth(cgImageRef);
GLuint height = (GLuint)CGImageGetHeight(cgImageRef);
CGRect rect = CGRectMake(0, 0, width, height);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc(width * height * 4);
CGContextRef context = CGBitmapContextCreate(imageData, width, height, 8, width * 4, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGContextTranslateCTM(context, 0, height);
CGContextScaleCTM(context, 1.0f, -1.0f);
CGColorSpaceRelease(colorSpace);
CGContextClearRect(context, rect);
CGContextDrawImage(context, rect, cgImageRef);
GLuint textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, 0);
CGContextRelease(context);
free(imageData);
return textureID;
}
//设置着色器
- (void)setupShaderProgramWidthName:(NSString *)name {
GLuint program = [self programWithShaderName:name];
glUseProgram(program);
GLuint positionSlot = glGetAttribLocation(program, "Position");
GLuint textureSlot = glGetAttribLocation(program, "Texture");
GLuint textureCoordSlot = glGetAttribLocation(program, "TextureCoord");
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, self.textureID);
glUniform1i(textureSlot, 0);
glEnableVertexAttribArray(positionSlot);
glVertexAttribPointer(positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(SenceVertex), NULL + offsetof(SenceVertex, positionCoord));
glEnableVertexAttribArray(textureCoordSlot);
glVertexAttribPointer(textureCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(SenceVertex), NULL + offsetof(SenceVertex, textureCoord));
self.program = program;
}
- (GLuint)programWithShaderName:(NSString *)shaderName {
GLuint vertexShader = [self compileShaderWithName:shaderName type:GL_VERTEX_SHADER];
GLuint fragmentShader = [self compileShaderWithName:shaderName type:GL_FRAGMENT_SHADER];
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glLinkProgram(program);
GLint linkSuccess;
glGetProgramiv(program, GL_LINK_STATUS, &linkSuccess);
if (linkSuccess == GL_FALSE) {
GLchar messages[250];
glGetProgramInfoLog(program, sizeof(messages), 0, &messages[0]);
NSString *messageString = [NSString stringWithUTF8String:messages];
NSAssert(NO, @"program link 失败 %@", messageString);
exit(1);
}
return program;
}
- (GLuint)compileShaderWithName:(NSString *)name type:(GLenum)shaderType {
NSString *shaderPath = [[NSBundle mainBundle] pathForResource:name ofType:shaderType == GL_VERTEX_SHADER ? @"vsh" : @"fsh" ];
NSError *error;
NSString *shaderString = [NSString stringWithContentsOfFile:shaderPath encoding:NSUTF8StringEncoding error:&error];
if (!shaderString) {
NSAssert(NO, @"读取shader失败");
exit(1);
}
GLuint shader = glCreateShader(shaderType);
const char *shaderStringUTF8 = [shaderString UTF8String];
int shaderStringLength = (int)[shaderString length];
glShaderSource(shader, 1, &shaderStringUTF8, &shaderStringLength);
glCompileShader(shader);
GLint compileSuccess;
glGetShaderiv(shader, GL_COMPILE_STATUS, &compileSuccess);
if (compileSuccess == GL_FALSE) {
GLchar messages[250];
glGetShaderInfoLog(shader, sizeof(messages), 0, &messages[0]);
NSString *messageString = [NSString stringWithUTF8String:messages];
NSAssert(NO, @"shader编译失败： %@", messageString);
exit(1);
}
return shader;
}
// 返回某个纹理对应的 UIImage，调用前先绑定对应的帧缓存
- (UIImage *)imageFromTextureWithWidth:(int)width height:(int)height {
int size = width * height * 4;
GLubyte *buffer = malloc(size);
glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, size, NULL);
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * width;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
// 此时的 imageRef 是上下颠倒的，调用 CG 的方法重新绘制一遍，刚好翻转过来
UIGraphicsBeginImageContext(CGSizeMake(width, height));
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
free(buffer);
self.imageView.image = image;
return image;
}
// 获取渲染缓存区的宽
- (GLint)drawableWidth {
GLint backingWith;
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &backingWith);
return backingWith;
}
// 获取渲染缓存区的高
- (GLint)drawableHeight {
GLint backingHeight;
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &backingHeight);
return backingHeight;
}
@end
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