闲来无事,最近在研究OpenGLES的东西,发现在游戏开发 音视频 直播等都有着广泛的应用 觉得这是一个可以去研究的方向 这只是我的一个想法 有待考证 如果有什么不对的地方 非常大家在评论区 大家一起交流 批评指正我的误解和不对的地方 废话不说 来干货
图片加载有主要是两种方式 一个是imageNamed 一个是imageWithContenFIle 。imageNamed会缓存到系统的cache中 对于 小图不错 但是对于大图 缓存太多就不太容易被释放 imageWithContenFIle 是直接采用的OpengGL 实现降图片已纹理的形式 渲染到View上面去的 主要是通过OpenGL的定点着色器和片段着色器去修改 代码示例如下 了解更多的内容 可以去学习下OpenGL 函数和 矩阵等相关的一些内容 最终的效果图片
https://github.com/evernoteHW/OpenglImageDemo
重写OpenGLView
<pre><code class="objc">
@interface OpenGLView(){
NSMutableArray * _vboArray;
KSMatrix4 _rotationMatrix;
}
@end
@implementation OpenGLView
#pragma mark- Initilize GL
+ (Class)layerClass {
// Support for OpenGL ES
return [CAEAGLLayer class];
}
- (void)setupLayer
{
_eaglLayer = (CAEAGLLayer*) self.layer;
// Make CALayer visibale
_eaglLayer.opaque = YES;
// Set drawable properties
_eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
}
- (void)setupContext
{
// Set OpenGL version, here is OpenGL ES 2.0
EAGLRenderingAPI api = kEAGLRenderingAPIOpenGLES2;
_context = [[EAGLContext alloc] initWithAPI:api];
if (!_context) {
NSLog(@" >> Error: Failed to initialize OpenGLES 2.0 context");
exit(1);
}
// Set OpenGL context
if (![EAGLContext setCurrentContext:_context]) {
_context = nil;
NSLog(@" >> Error: Failed to set current OpenGL context");
exit(1);
}
}
- (void)setupBuffers
{
// Setup color render buffer
glGenRenderbuffers(1, &_colorRenderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderBuffer);
[_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:_eaglLayer];
// Setup depth render buffer
int width, height;
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &width);
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &height);
// Create a depth buffer that has the same size as the color buffer.
glGenRenderbuffers(1, &_depthRenderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);
// Setup frame buffer
//
glGenFramebuffers(1, &_frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, _frameBuffer);
// Attach color render buffer and depth render buffer to frameBuffer
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
GL_RENDERBUFFER, _colorRenderBuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
GL_RENDERBUFFER, _depthRenderBuffer);
// Set color render buffer as current render buffer
glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderBuffer);
}
- (void)destoryBuffer:(GLuint *)buffer
{
if (buffer && *buffer != 0) {
glDeleteRenderbuffers(1, buffer);
*buffer = 0;
}
}
- (void)destoryBuffers
{
[self destoryBuffer: &_depthRenderBuffer];
[self destoryBuffer: &_colorRenderBuffer];
[self destoryBuffer: &_frameBuffer];
}
- (void)cleanup
{
[self destoryBuffers];
if (_programHandle != 0) {
glDeleteProgram(_programHandle);
_programHandle = 0;
}
if (_context && [EAGLContext currentContext] == _context)
[EAGLContext setCurrentContext:nil];
_context = nil;
}
- (void)setupProgram
{
// Load shaders
//
NSString * vertexShaderPath = [[NSBundle mainBundle] pathForResource:@"VertexShader"
ofType:@"glsl"];
NSString * fragmentShaderPath = [[NSBundle mainBundle] pathForResource:@"FragmentShader"ofType:@"glsl"];
_programHandle = [GLESUtils loadProgram:vertexShaderPath
withFragmentShaderFilepath:fragmentShaderPath];
if (_programHandle == 0) {
NSLog(@" >> Error: Failed to setup program.");
return;
}
glUseProgram(_programHandle);
[self getSlotsFromProgram];
}
#pragma mark - Light
- (void)setupLights
{
// Set up some default material parameters.
//
glUniform3f(_ambientSlot, 0.04f, 0.04f, 0.04f);
glUniform3f(_specularSlot, 0.5, 0.5, 0.5);
glUniform1f(_shininessSlot, 50)
// Initialize various state.
//
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_normalSlot);
glUniform3f(_lightPositionSlot, 1.0, 1.0, 5.0);
glVertexAttrib3f(_diffuseSlot, 0.8, 0.8, 0.8);
}
#pragma mark - Texture
- (void)updateTextureParameter
{
// It can be GL_NICEST or GL_FASTEST or GL_DONT_CARE. GL_DONT_CARE by default.
//
glHint(GL_GENERATE_MIPMAP_HINT, GL_NICEST);
//单独为纹理缩放指定不同的过滤算法
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
//为纹理坐标系中每条坐标轴设定不同的wrapping模式
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
}
- (void)setupTextures
{
glActiveTexture(GL_TEXTURE0);
glEnableVertexAttribArray(_textureCoordSlot);
glUniform1i(_samplerSlot, 0);
}
#pragma mark - Draw object
- (void)getSlotsFromProgram
{
// Get the attribute and uniform slot from program
//
_projectionSlot = glGetUniformLocation(_programHandle, "projection");
_modelViewSlot = glGetUniformLocation(_programHandle, "modelView");
_normalMatrixSlot = glGetUniformLocation(_programHandle, "normalMatrix");
_lightPositionSlot = glGetUniformLocation(_programHandle, "vLightPosition");
_ambientSlot = glGetUniformLocation(_programHandle, "vAmbientMaterial");
_specularSlot = glGetUniformLocation(_programHandle, "vSpecularMaterial");
_shininessSlot = glGetUniformLocation(_programHandle, "shininess");
_positionSlot = glGetAttribLocation(_programHandle, "vPosition");
_normalSlot = glGetAttribLocation(_programHandle, "vNormal");
_diffuseSlot = glGetAttribLocation(_programHandle, "vDiffuseMaterial");
_textureCoordSlot = glGetAttribLocation(_programHandle, "vTextureCoord");
_samplerSlot = glGetUniformLocation(_programHandle, "Sampler");
}
- (void)setupProjection
{
float width = self.frame.size.width;
float height = self.frame.size.height;
// Generate a perspective matrix with a 60 degree FOV
ksMatrixLoadIdentity(&_projectionMatrix);
float aspect = width / height;
ksPerspective(&_projectionMatrix, 60.0, aspect, 4.0f, 12.0f);
// Load projection matrix
glUniformMatrix4fv(_projectionSlot, 1, GL_FALSE, (GLfloat*)&_projectionMatrix.m[0][0]);
//glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
}
- (void)resetRotation
{
ksMatrixLoadIdentity(&_rotationMatrix);
}
- (void)updateSurface
{
ksMatrixLoadIdentity(&_modelViewMatrix);
ksTranslate(&_modelViewMatrix, 0.0, 0.0, -8);
ksMatrixMultiply(&_modelViewMatrix, &_rotationMatrix, &_modelViewMatrix);
// Load the model-view matrix
glUniformMatrix4fv(_modelViewSlot, 1, GL_FALSE, (GLfloat)&_modelViewMatrix.m[0][0]);
// Load the normal matrix.
// It's orthogonal, so its Inverse-Transpose is itself!
//
KSMatrix3 normalMatrix3;
ksMatrix4ToMatrix3(&normalMatrix3, &_modelViewMatrix);
glUniformMatrix3fv(_normalMatrixSlot, 1, GL_FALSE, (GLfloat)&normalMatrix3.m[0][0]);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, [self createTexture:@"flower.jpg"]);
[self updateTextureParameter];
}
- (GLuint)createTexture:(NSString )textureFile
{
NSString resourcePath = [[NSBundle mainBundle] resourcePath];
NSString* fullPath = [resourcePath stringByAppendingPathComponent:textureFile];
UIImage* uiImage = [UIImage imageWithContentsOfFile:fullPath];
CGImageRef cgImage = uiImage.CGImage;
CGSize originalSize = CGSizeZero;
originalSize.width = CGImageGetWidth(cgImage);
originalSize.height = CGImageGetHeight(cgImage);
int byteCount = originalSize.width * originalSize.height * 4;
unsigned char* data = (unsigned char) calloc(byteCount, 1);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;
CGContextRef context = CGBitmapContextCreate(data,
originalSize.width,
originalSize.height,
8,
4 * originalSize.width,
colorSpace,
bitmapInfo);
CGColorSpaceRelease(colorSpace);
CGRect rect = CGRectMake(0, 0, originalSize.width, originalSize.height);
CGContextDrawImage(context, rect, uiImage.CGImage);
CGContextRelease(context);
NSData imageData = [NSData dataWithBytesNoCopy:data length:byteCount freeWhenDone:YES];
GLuint textureHandle = 0;
glGenTextures(1, &textureHandle);
glBindTexture(GL_TEXTURE_2D, textureHandle);
void pixels = (void) [imageData bytes];
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, originalSize.width, originalSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
glGenerateMipmap(GL_TEXTURE_2D);
return textureHandle;
}
- (void)drawSurface
{
const GLfloat vertices[] = {
-2.0, -2.0, 2.0, 0, 0, 1, 0, 1,
-2.0, 2.0, 2.0, 0, 0, 1, 0, 0,
2.0, 2.0, 2.0, 0, 0, 1, 1, 0,
2.0, -2.0, 2.0, 0, 0, 1, 1, 1,
};
const GLushort indices[] = {
// Front face
0, 3, 1, 3, 2, 1
};
// Create the VBO for the vertice.
//
int vertexSize = 8;
GLuint vertexBuffer;
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
// Create the VBO for the triangle indice
int triangleIndexCount = sizeof(indices)/sizeof(indices[0]);
GLuint triangleIndexBuffer;
glGenBuffers(1, &triangleIndexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, triangleIndexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, triangleIndexCount * sizeof(GLushort), indices, GL_STATIC_DRAW);
//////////////////////////
int stride = vertexSize * sizeof(GLfloat);
const GLvoid* normalOffset = (const GLvoid)(3 * sizeof(GLfloat));
const GLvoid texCoordOffset = (const GLvoid*)(6 * sizeof(GLfloat));
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, stride, 0);
glVertexAttribPointer(_normalSlot, 3, GL_FLOAT, GL_FALSE, stride, normalOffset);
glVertexAttribPointer(_textureCoordSlot, 2, GL_FLOAT, GL_FALSE, stride, texCoordOffset);
// Draw the triangles.
//
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, triangleIndexBuffer);
glDrawElements(GL_TRIANGLES, triangleIndexCount, GL_UNSIGNED_SHORT, 0);
}
- (void)render
{
if (_context == nil)
return;
glClearColor(0.0f, 1.0f, 0.0f, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Setup viewport
//
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
[self updateSurface];
[self drawSurface];
[_context presentRenderbuffer:GL_RENDERBUFFER];
}
#pragma mark
- (instancetype)initWithFrame:(CGRect)frame{
self = [super initWithFrame:frame];
if (self) {
[self setupLayer];
[self setupContext];
[self setupProgram];
[self setupProjection];
[self setupLights];
[self setupTextures];
[self resetRotation];
[GLESUtils printExtensions];
}
return self;
}
- (void)layoutSubviews
{
[EAGLContext setCurrentContext:_context];
glUseProgram(_programHandle);
[self destoryBuffers];
[self setupBuffers];
[self render];
}
@end</code></pre>
