iOS OpenGL ES 2.0：离屏渲染并将结果保存到UIImage
我正在使用OpenGL ES来渲染一些特殊效果，我不想把这个显示给用户，我只是想将结果保存为一个UIImage，任何人都可以帮我吗？
这是我正在使用的代码，我可以得到一个图像，其中包含我使用的红色清除颜色，但没有显示几何graphics。
#import "RendererGL.h" #import <GLKit/GLKit.h> #import <UIKit/UIKit.h> #import <OpenGLES/EAGL.h> #import <OpenGLES/EAGLDrawable.h> #import <OpenGLES/ES2/glext.h> #import <QuartzCore/QuartzCore.h> static NSInteger WIDTH_IN_PIXEL = 400; static NSInteger HEIGHT_IN_PIXEL = 300; typedef struct { GLKVector3 positionCoords; } SceneVertex; static const SceneVertex vertices[] = { {{-0.5f, -0.5f, 0.0}}, // lower left corner {{ 0.5f, -0.5f, 0.0}}, // lower right corner {{-0.5f, 0.5f, 0.0}} // upper left corner }; @implementation RendererGL { EAGLContext* _myContext; GLuint _framebuffer; GLuint _colorRenderbuffer; GLuint _depthRenderbuffer; GLuint _vertexBufferID; GLKBaseEffect *_baseEffect; } - (id) init { self = [super init]; if (self) { _myContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2]; [EAGLContext setCurrentContext:_myContext]; [self setupOffscreenBuffer]; [self setUpEffect]; [self renderImage]; [self saveImage]; //this do works, since I get an image, but the image only contains the red color I used to clear } return self; } -(void)setUpEffect { _baseEffect = [[GLKBaseEffect alloc] init]; _baseEffect.useConstantColor = GL_TRUE; _baseEffect.constantColor = GLKVector4Make(0.0f, 0.0f, 1.0f, 1.0f); } //this code is from apples document -(void)setupOffscreenBuffer { glGenFramebuffers(1, &_framebuffer); glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer); glGenRenderbuffers(1, &_colorRenderbuffer); glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderbuffer); glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA4, WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorRenderbuffer); glGenRenderbuffers(1, &_depthRenderbuffer); glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderbuffer); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderbuffer); GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER) ; if(status != GL_FRAMEBUFFER_COMPLETE) { NSLog(@"failed to make complete framebuffer object %x", status); } } - (void) renderImage { GLenum error = GL_NO_ERROR; glClearColor(1, 0, 0, 1); //red clear color, this can be seen glClear(GL_COLOR_BUFFER_BIT); glEnable(GL_DEPTH_TEST); [_baseEffect prepareToDraw]; glGenBuffers(1, &_vertexBufferID); glBindBuffer(GL_ARRAY_BUFFER, _vertexBufferID); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); error = glGetError(); if (error != GL_NO_ERROR) { NSLog(@"error happend, error is %d, line %d",error,__LINE__); } glEnableVertexAttribArray(GLKVertexAttribPosition); glVertexAttribPointer(GLKVertexAttribPosition,3,GL_FLOAT, GL_FALSE, sizeof(SceneVertex), NULL); glDrawArrays(GL_TRIANGLES,0,3); error = glGetError(); if (error != GL_NO_ERROR) { NSLog(@"error happend, error is %d, line %d",error,__LINE__); } glFinish(); error = glGetError(); if (error != GL_NO_ERROR) { NSLog(@"error happend, error is %d, line %d",error,__LINE__); } } -(void)saveImage { GLenum error = GL_NO_ERROR; NSInteger x = 0, y = 0; NSInteger dataLength = WIDTH_IN_PIXEL * HEIGHT_IN_PIXEL * 4; GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte)); glPixelStorei(GL_PACK_ALIGNMENT, 4); glReadPixels(x, y, WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL, GL_RGBA, GL_UNSIGNED_BYTE, data); NSData *pixelsRead = [NSData dataWithBytes:data length:dataLength]; error = glGetError(); if (error != GL_NO_ERROR) { NSLog(@"error happend, error is %d, line %d",error,__LINE__); } CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL); CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB(); CGImageRef iref = CGImageCreate(WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL, 8, 32, WIDTH_IN_PIXEL * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast, ref, NULL, true, kCGRenderingIntentDefault); UIGraphicsBeginImageContext(CGSizeMake(WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL)); CGContextRef cgcontext = UIGraphicsGetCurrentContext(); CGContextSetBlendMode(cgcontext, kCGBlendModeCopy); CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, WIDTH_IN_PIXEL, HEIGHT_IN_PIXEL), iref); UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); NSData *d = UIImageJPEGRepresentation(image, 1); NSString *documentDirPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0]; static NSInteger imageNO = 1; imageNO++; NSString *savingPath = [documentDirPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%d.jpg",imageNO]]; BOOL succ = [d writeToFile:savingPath atomically:NO]; //is succeeded UIGraphicsEndImageContext(); free(data); CFRelease(ref); CFRelease(colorspace); CGImageRelease(iref); } @end 我有一个非常类似的问题 – 呈现一些线条，并获得UIImage。 我使用了OpenGL ES 1.1和多重采样。 我删除了一些不涉及渲染和一些OpenGL错误检查的附加代码。 你可以在这里find完整的代码： OSPRendererGL 。 另外，对不起，我的一个所有的方法。
@interface OSPRendererGL { EAGLContext* myContext; GLuint framebuffer; GLuint colorRenderbuffer; GLuint depthRenderbuffer; GLuint _vertexArray; GLuint _vertexBuffer; GLuint resolveFramebuffer; GLuint msaaFramebuffer, msaaRenderbuffer, msaaDepthbuffer; int width; int height; } @implementation OSPRendererGL - (id) init { self = [super init]; if (self) { myContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1]; [EAGLContext setCurrentContext:myContext]; [self setupOpenGL]; [EAGLContext setCurrentContext:nil]; width = 256; height = 256; } return self; } -(void) setupOpenGL { glGenFramebuffersOES(1, &framebuffer); glBindFramebufferOES(GL_FRAMEBUFFER_OES, framebuffer); glGenRenderbuffersOES(1, &colorRenderbuffer); glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer); glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_RGBA8_OES, width, height); glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, colorRenderbuffer); glGenRenderbuffersOES(1, &depthRenderbuffer); glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer); glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, width, height); glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthRenderbuffer); glGenFramebuffersOES(1, &msaaFramebuffer); glGenRenderbuffersOES(1, &msaaRenderbuffer); glBindFramebufferOES(GL_FRAMEBUFFER_OES, msaaFramebuffer); glBindRenderbufferOES(GL_RENDERBUFFER_OES, msaaRenderbuffer); glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER_OES, 4, GL_RGBA8_OES, width, height); glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, msaaRenderbuffer); glGenRenderbuffersOES(1, &msaaDepthbuffer); glBindRenderbufferOES(GL_RENDERBUFFER_OES, msaaDepthbuffer); glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER_OES, 4, GL_DEPTH_COMPONENT16_OES, width, height); glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, msaaDepthbuffer); } -(UIImage *) renderImageAtZoom:(int)zoom { CGRect b = CGRectMake(0, 0, width, height); OSPCoordinateRect r = OSPRectForMapAreaInRect([self mapArea], b); double_scale = b.size.width / r.size.x; double scale = 1.0/_scale; [EAGLContext setCurrentContext:myContext]; glBindFramebuffer(GL_FRAMEBUFFER_OES, msaaFramebuffer); glBindRenderbufferOES(GL_RENDERBUFFER_OES, msaaRenderbuffer); glViewport(0, 0, width, height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(0.0f, 256.0f, 256.0f, 0.0f, 1.0f, -1.0f); glMatrixMode(GL_MODELVIEW); glPushMatrix(); glScalef(_scale, _scale, 1); glTranslatef(-r.origin.x, -r.origin.y, 0); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glEnable(GL_LINE_SMOOTH); glEnable(GL_POINT_SMOOTH); glEnable(GL_BLEND); glClearColor(1, 1, 1, 1); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // rendering here glPopMatrix(); // msaa glBindFramebufferOES(GL_READ_FRAMEBUFFER_APPLE, msaaFramebuffer); glBindFramebufferOES(GL_DRAW_FRAMEBUFFER_APPLE, framebuffer); glResolveMultisampleFramebufferAPPLE(); glBindFramebuffer(GL_FRAMEBUFFER_OES, framebuffer); glBindRenderbufferOES(GL_RENDERBUFFER, colorRenderbuffer); // grabbing image from FBO GLint backingWidth, backingHeight; glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth); glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight); NSInteger x = 0, y = 0; NSInteger dataLength = width * height * 4; GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte)); glPixelStorei(GL_PACK_ALIGNMENT, 4); glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data); CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL); CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB(); CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast, ref, NULL, true, kCGRenderingIntentDefault); UIGraphicsBeginImageContext(CGSizeMake(width, height)); CGContextRef cgcontext = UIGraphicsGetCurrentContext(); CGContextSetBlendMode(cgcontext, kCGBlendModeCopy); CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, width, height), iref); UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); free(data); CFRelease(ref); CFRelease(colorspace); CGImageRelease(iref); [EAGLContext setCurrentContext:nil]; return image; }
我没有看到eglSwapBuffers（）的调用。 即使渲染到渲染缓冲区，也需要在PowerVR上开始渲染帧。 请参阅示例代码：
http://processors.wiki.ti.com/index.php/Render_to_Texture_with_OpenGL_ES