iphone - 如何在不使用 iOS 5.0 特定功能的情况下重写 GLCameraRipple 示例？

Question

如何重写 Apple 的 GLCameraRipple example这样它就不需要 iOS 5.0 了吗？

我需要让它在 iOS 4.x 上运行，所以我不能使用 CVOpenGLESTextureCacheCreateTextureFromImage。我该怎么办？

作为后续，我使用下面的代码提供 YUV 数据而不是 RGB，但是图片不正确，屏幕是绿色的。似乎 UV 平面不起作用。

CVPixelBufferLockBaseAddress(cameraFrame, 0);
int bufferHeight = CVPixelBufferGetHeight(cameraFrame);
int bufferWidth = CVPixelBufferGetWidth(cameraFrame);

// Create a new texture from the camera frame data, display that using the shaders
glActiveTexture(GL_TEXTURE0);
glGenTextures(1, &_lumaTexture);
glBindTexture(GL_TEXTURE_2D, _lumaTexture);

glUniform1i(UNIFORM[Y], 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// This is necessary for non-power-of-two textures
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, bufferWidth, bufferHeight, 0, GL_LUMINANCE, 
             GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddressOfPlane(cameraFrame, 0));

glActiveTexture(GL_TEXTURE1);
glGenTextures(1, &_chromaTexture);
glBindTexture(GL_TEXTURE_2D, _chromaTexture);
glUniform1i(UNIFORM[UV], 1);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// This is necessary for non-power-of-two textures
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

// Using BGRA extension to pull in video frame data directly
glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE_ALPHA, bufferWidth/2, bufferHeight/2, 0, GL_LUMINANCE_ALPHA, 
             GL_UNSIGNED_BYTE, CVPixelBufferGetBaseAddressOfPlane(cameraFrame, 1));

[self drawFrame];

glDeleteTextures(1, &_lumaTexture);
glDeleteTextures(1, &_chromaTexture);

CVPixelBufferUnlockBaseAddress(cameraFrame, 0);

我该如何解决这个问题？

Answer 1

如果您将像素格式从 kCVPixelFormatType_420YpCbCr8BiPlanarFullRange 切换为 kCVPixelFormatType_32BGRA(在 RippleViewController 的第 315 行)，则 captureOutput:didOutputSampleBuffer:fromConnection: 将收到一个样本缓冲区，其中的图像缓冲区可以通过 glTexImage2D(或者 glTexSubImage2D 如果你想保持你的纹理大小为 2 的幂)直接上传到 OpenGL。这是可行的，因为迄今为止所有 iOS 设备都支持 GL_APPLE_texture_format_BGRA8888 扩展，允许您指定 GL_BGRA 的其他非标准格式。

因此，您需要使用 glGenTextures 提前在某处创建一个纹理，并将第 235 行替换为类似以下内容:

glBindTexture(GL_TEXTURE_2D, myTexture);

CVPixelBufferLockBaseAddress(pixelBuffer);
glTexSubImage2D(GL_TEXTURE_2D, 0,
      0, 0,
      CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer),
      GL_BGRA, GL_UNSIGNED_BYTE, 
      CVPixelBufferGetBaseAddress(pixelBuffer));

CVPixelBufferUnlockBaseAddress(pixelBuffer);

您可能需要检查 CVPixelBufferGetBytesPerRow 的结果是 CVPixelBufferGetWidth 的四倍；我从文档中不确定它是否总是保证(实际上，这可能意味着它不是)，但只要它是四的倍数，你就可以提供 CVPixelBufferGetBytesPerRow 除以四作为你的假装宽度，假设你上传的是一张子图片。

编辑:为了回应下面作为评论发布的后续问题，如果您想坚持接收帧并使它们在 YUV 中可供 GPU 使用，那么代码在视觉上会变得难看，因为您返回的是指向各种 channel 组件的结构，但你会想要这样的东西:

// lock the base address, pull out the struct that'll show us where the Y
// and CbCr information is actually held
CVPixelBufferLockBaseAddress(pixelBuffer);
CVPlanarPixelBufferInfo_YCbCrBiPlanar *info = CVPixelBufferGetBaseAddress(imageBuffer);

// okay, upload Y. You'll want to communicate this texture to the
// SamplerY uniform within the fragment shader.
glBindTexture(GL_TEXTURE_2D, yTexture);

uint8_t *yBaseAddress = (uint8_t *)info + EndianU32_BtoN(info->componentInfoY.offset);
uint32_t yRowBytes = EndianU32_BtoN(info->componentInfoY.rowBytes);

/* TODO: check that yRowBytes is equal to CVPixelBufferGetWidth(pixelBuffer);
   otherwise you'll need to shuffle memory a little */

glTexSubImage2D(GL_TEXTURE_2D, 0,
      0, 0,
      CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer),
      GL_LUMINANCE, GL_UNSIGNED_BYTE, 
      yBaseAddress);

// we'll also need to upload the CbCr part of the buffer, as a two-channel
// (ie, luminance + alpha) texture. This texture should be supplied to
// the shader for the SamplerUV uniform.
glBindTexture(GL_TEXTURE_2D, uvTexture);

uint8_t *uvBaseAddress = (uint8_t *)info + EndianU32_BtoN(info->componentInfoCbCr.offset);
uint32_t uvRowBytes = EndianU32_BtoN(info->componentInfoCbCr.rowBytes);

/* TODO: a check on uvRowBytes, as above */

glTexSubImage2D(GL_TEXTURE_2D, 0,
      0, 0,
      CVPixelBufferGetWidth(pixelBuffer)/2, CVPixelBufferGetHeight(pixelBuffer)/2,
      GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, 
      uvBaseAddress);

CVPixelBufferUnlockBaseAddress(pixelBuffer);