2014/10/15 下午 10:09:40

iphone Programming Glossary: glreadpixels

http://stackoverflow.com/questions/10455329/opengl-es-2d-rendering-into-image

of that scene to use outside of OpenGL ES you have two main options. The first is to simply render your scene and use glReadPixels to grab RGBA data for the scene and place it in a byte array like in the following GLubyte rawImagePixels GLubyte malloc.. the scene and place it in a byte array like in the following GLubyte rawImagePixels GLubyte malloc totalBytesForImage glReadPixels 0 0 int currentFBOSize.width int currentFBOSize.height GL_RGBA GL_UNSIGNED_BYTE rawImagePixels Do something with the image.. 0 and then you can just read directly from the bytes that back this texture in BGRA format not the RGBA of glReadPixels using something like CVPixelBufferLockBaseAddress renderTarget 0 _rawBytesForImage GLubyte CVPixelBufferGetBaseAddress renderTarget..

Drawing into OpenGL ES framebuffer and getting UIImage from it on iPhone

http://stackoverflow.com/questions/10936157/drawing-into-opengl-es-framebuffer-and-getting-uiimage-from-it-on-iphone

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..

How do I grab an image from my EAGLLayer ?

http://stackoverflow.com/questions/314254/how-do-i-grab-an-image-from-my-eagllayer

I'm looking for way to grab the content of my opengl as UIImage and then save it into a file. I'm now giving glReadPixels a try though I'm not sure I'm doing the right thing as of what kind of malloc I should be doing. I gather that on OSX it's.. share improve this question All OpenGL ES complient GL implementations have to support GL_RGBA as a parameter to glReadPixels. If your OpenGL Es supports the GL_IMPLEMENTATION_COLOR_READ_FORMAT_OES extension you can also query the native format... If your OpenGL Es supports the GL_IMPLEMENTATION_COLOR_READ_FORMAT_OES extension you can also query the native format. glReadPixels will understand this format as a parameter to glReadPixels and allows you to directly get the pixel data in native format...

how to record screen video as like Talking Tomcat application does in iphone?

http://stackoverflow.com/questions/6980370/how-to-record-screen-video-as-like-talking-tomcat-application-does-in-iphone

trying to do same thing as Talking tomcat app for iphone..recording the video then playing it etc... i m using glReadPixels for reading framebuffer data and then writing it to video with the help of AVAssetWriter in AVFoundation framwork. But reading.. framwork. But reading the data on each drawing decreases the FPS from around 30 35 to 2 3 only while using glReadPixels. i think Talking tomcat is also made with the help of Opengl ES it also has the video recording facility but it doesnot..

iPhone take augmented reality screenshot with AVCaptureVideoPreviewLayer

http://stackoverflow.com/questions/8980847/iphone-take-augmented-reality-screenshot-with-avcapturevideopreviewlayer

data GLubyte malloc dataLength sizeof GLubyte Read pixel data from the framebuffer glPixelStorei GL_PACK_ALIGNMENT 4 glReadPixels x y width height GL_RGBA GL_UNSIGNED_BYTE data Create a CGImage with the pixel data If your OpenGL ES content is opaque..

Faster alternative to glReadPixels in iPhone OpenGL ES 2.0

http://stackoverflow.com/questions/9550297/faster-alternative-to-glreadpixels-in-iphone-opengl-es-2-0

alternative to glReadPixels in iPhone OpenGL ES 2.0 Is there any faster way to access the frame buffer than using glReadPixels I would need read only.. alternative to glReadPixels in iPhone OpenGL ES 2.0 Is there any faster way to access the frame buffer than using glReadPixels I would need read only access to a small rectangular rendering area in the frame buffer to process the data further in CPU... pixels for that scene will be contained within your CVPixelBufferRef so there will be no need to pull them down using glReadPixels . This is much much faster than using glReadPixels in my benchmarks. I found that on my iPhone 4 glReadPixels was the bottleneck..

Capturing EAGLview content WITH alpha channel on iPhone

http://stackoverflow.com/questions/962390/capturing-eaglview-content-with-alpha-channel-on-iphone

Let me share some code with you I found somewhere else CGImageRef glToUIImage unsigned char buffer 320 480 4 glReadPixels 0 0 320 480 GL_RGBA GL_UNSIGNED_BYTE buffer CGDataProviderRef ref CGDataProviderCreateWithData NULL buffer 320 480 4 NULL..

Record the drawing as a m4v video file - OpenGL

http://stackoverflow.com/questions/9661259/record-the-drawing-as-a-m4v-video-file-opengl

you'll need to provide frames to the writer in BGRA format not the RGBA you get from reading the screen using glReadPixels . In my case I used a color swizzling shader to convert from RGBA to BGRA before reading but you don't have that option.. YES You need to use BGRA for the video in order to get realtime encoding. I use a color swizzling shader to line up glReadPixels' normal RGBA output with the movie input's BGRA. NSDictionary sourcePixelBufferAttributesDictionary NSDictionary dictionaryWithObjectsAndKeys.. CVPixelBufferLockBaseAddress pixel_buffer 0 GLubyte pixelBufferData GLubyte CVPixelBufferGetBaseAddress pixel_buffer glReadPixels 0 0 videoSize.width videoSize.height GL_RGBA GL_UNSIGNED_BYTE pixelBufferData May need to add a check here because if two..

Saving imageRef from GLPaint creates completely black image

http://stackoverflow.com/questions/9857912/saving-imageref-from-glpaint-creates-completely-black-image

NSInteger myDataLength w h 4 s s allocate array and read pixels into it. GLubyte buffer GLubyte malloc myDataLength glReadPixels 0 0 w s h s GL_RGBA GL_UNSIGNED_BYTE buffer gl renders upside down so swap top to bottom into new array. there's gotta be..