小型电裁剪刀_手动裁剪

小型电裁剪刀_手动裁剪由于简书经常打不开,或者打开慢,不靠谱,还是把文章迁移到CSDN吧。简书链接:https://www.jianshu.com/p/8c6508cab763有时候想对摄像头采集的视频流进行区域裁剪,可以使用libyuv这个库,原理就是先把NV12转换为i420,对i420做裁剪,然后再把i420转换为NV12,NV12再转换为CVPixelBufferRef,CVPixelBufferRef再转…

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由于简书经常打不开,或者打开慢,不靠谱,还是把文章迁移到CSDN吧。
简书链接:https://www.jianshu.com/p/8c6508cab763
有时候想对摄像头采集的视频流进行区域裁剪,可以使用libyuv这个库,原理就是先把NV12转换为i420,对i420做裁剪,然后再把i420转换为NV12,NV12再转换为CVPixelBufferRef,CVPixelBufferRef再转换为CMSampleBufferRef。

这里有几个注意点:
1.iOS13使用了64位对齐,也就是步长是64的倍数。而之前的版本使用的是16位对齐。
2.使用 libyuv::ConvertToI420 方法时,src_width需要填入步长而不是宽度,因为yuv内部要根据步长来取U、V数据,如果是填入的宽度,那么就会取值位移错误,导致转换失真。
3.因为我是直接NV12数据转换的,所以填写的类型是:libyuv::FOURCC_NV12。应该根据当前数据的类型选择对应的格式。
4.NV12转换为CVPixelBufferRef时,填入对应的步长:nv12_plane1_stride。

关于步长解释:https://www.jianshu.com/p/eace8c08b169

一:对NV12裁剪代码如下:
+ (CVPixelBufferRef)convertNV12ToI420Screenshots:(CMSampleBufferRef)sampleBufRef screenshotsFrame:(CGRect)screenshotsFrame {
    int screenshots_x = screenshotsFrame.origin.x;
    int screenshots_y = screenshotsFrame.origin.y;
    int screenshots_width = screenshotsFrame.size.width;
    int screenshots_hight = screenshotsFrame.size.height;
    // 确保宽高是偶数
    if (screenshots_width % 2 != 0) {
        screenshots_width++;
    }
    if (screenshots_hight % 2 != 0) {
        screenshots_hight++;
    }
    //CVPixelBufferRef是CVImageBufferRef的别名,两者操作几乎一致。
    //获取CMSampleBuffer的图像地址
    CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBufRef);
    if (!pixelBuffer) {
        return nil;
    }
    //表示开始操作数据
    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
    //图像高度(像素)
    size_t buffer_width = CVPixelBufferGetWidth(pixelBuffer);
    size_t buffer_height = CVPixelBufferGetHeight(pixelBuffer);
    //获取CVImageBufferRef中的y数据
    uint8_t *src_y_frame = (unsigned char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
    //y stride
    size_t plane1_stride = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
    //uv stride
    size_t plane2_stride = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1);
    //y height
    size_t plane1_height = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0);
    //uv height
    size_t plane2_height = CVPixelBufferGetHeightOfPlane(pixelBuffer, 1);
    //y_size
    size_t plane1_size = plane1_stride * plane1_height;
    //uv_size
    size_t plane2_size = plane2_stride * plane2_height;
    //yuv_size(内存空间)
    size_t frame_size = plane1_size + plane2_size;
    
    // 截取区域不能超出原视频大小
    if (screenshots_x >= buffer_width ||
        screenshots_width > buffer_width ||
        screenshots_x + screenshots_width > buffer_width ||
        screenshots_y >= buffer_height ||
        screenshots_hight > buffer_height ||
        screenshots_y + screenshots_hight > buffer_height) {
        return nil;
    }
    
    // 1.NV12数据进行相应的裁剪
    // 步长必须是16的倍数,因为涉及到字节对齐,而且iOS13和之前的版本处理方式不一样,要注意
    int stride_length = 16;
    int scale_plane1_stride = screenshots_width;
    if ([UIDevice currentDevice].systemVersion.floatValue >= 13.0) {
        stride_length = 64;
    } else {
        stride_length = 16;
    }
    if ((screenshots_width % stride_length) != 0) {
        scale_plane1_stride = (screenshots_width / stride_length + 1) * stride_length;
    }
    
    int scale_plane2_stride = scale_plane1_stride;
    int scale_plane1_height = screenshots_hight;
    int scale_plane2_height = screenshots_hight / 2;
    int scale_plane1_size = scale_plane1_stride * scale_plane1_height;
    int scale_plane2_size = scale_plane2_stride * scale_plane2_height;
    int scale_frame_size = scale_plane1_size + scale_plane2_size;

    uint8* scale_buffer = (unsigned char *)malloc(scale_frame_size);
    uint8* scale_buffer_u = scale_buffer + scale_plane1_size;
    uint8* scale_buffer_v = scale_buffer_u + scale_plane1_size / 4;
    
    libyuv::ConvertToI420(/*const uint8 *src_frame*/ src_y_frame,
                          /*size_t src_size*/ frame_size,
                          /*uint8 *dst_y*/ scale_buffer,
                          /*int dst_stride_y*/ scale_plane1_stride,
                          /*uint8 *dst_u*/ scale_buffer_u,
                          /*int dst_stride_u*/ scale_plane1_stride >> 1,
                          /*uint8 *dst_v*/ scale_buffer_v,
                          /*int dst_stride_v*/ scale_plane1_stride >> 1,
                          /*int crop_x*/ screenshots_x,
                          /*int crop_y*/ screenshots_y,
                          /*int src_width*/ (int)plane1_stride, // 注意这里使用的是步长,不是宽度,因为yuv内部要根据步长来取U、V数据
                          /*int src_height*/ (int)buffer_height,
                          /*int crop_width*/ screenshots_width,
                          /*int crop_height*/ screenshots_hight,
                          /*enum RotationMode rotation*/ libyuv::kRotate0,
                          /*uint32 format*/ libyuv::FOURCC_NV12);
    
    // 2.把缩放后的I420数据转换为NV12
    int nv12_plane1_stride = scale_plane1_stride;
    int nv12_width = screenshots_width;
    int nv12_hight = screenshots_hight;
    int nv12_frame_size = scale_frame_size;
    
    uint8 *nv12_dst_y = (uint8 *)malloc(nv12_frame_size);
    uint8 *nv12_dst_uv = nv12_dst_y + nv12_plane1_stride * nv12_hight;

    libyuv::I420ToNV12(/*const uint8 *src_y*/ scale_buffer,
                       /*int src_stride_y*/ scale_plane1_stride,
                       /*const uint8 *src_u*/ scale_buffer_u,
                       /*int src_stride_u*/ scale_plane1_stride >> 1,
                       /*const uint8 *src_v*/ scale_buffer_v,
                       /*int src_stride_v*/ scale_plane1_stride >> 1,
                       /*uint8 *dst_y*/ nv12_dst_y,
                       /*int dst_stride_y*/ nv12_plane1_stride,
                       /*uint8 *dst_uv*/ nv12_dst_uv,
                       /*int dst_stride_uv*/ nv12_plane1_stride,
                       /*int width*/ nv12_width,
                       /*int height*/ nv12_hight);
    
    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
    free(scale_buffer);
    
    // 4.NV12转换为CVPixelBufferRef
    NSDictionary *pixelAttributes = @{(id)kCVPixelBufferIOSurfacePropertiesKey : @{}};
    CVPixelBufferRef dstPixelBuffer = NULL;
    CVReturn result = CVPixelBufferCreate(kCFAllocatorDefault,
                                          nv12_width, nv12_hight, kCVPixelFormatType_420YpCbCr8BiPlanarFullRange,
                                          (__bridge CFDictionaryRef)pixelAttributes, &dstPixelBuffer);

    CVPixelBufferLockBaseAddress(dstPixelBuffer, 0);
    uint8_t *yDstPlane = (uint8*)CVPixelBufferGetBaseAddressOfPlane(dstPixelBuffer, 0);
    memcpy(yDstPlane, nv12_dst_y, nv12_plane1_stride * nv12_hight);
    uint8_t *uvDstPlane = (uint8*)CVPixelBufferGetBaseAddressOfPlane(dstPixelBuffer, 1);
    memcpy(uvDstPlane, nv12_dst_uv, nv12_plane1_stride * nv12_hight / 2);
    if (result != kCVReturnSuccess) {
        NSLog(@"Unable to create cvpixelbuffer %d", result);
    }
    CVPixelBufferUnlockBaseAddress(dstPixelBuffer, 0);

    free(nv12_dst_y);

    return dstPixelBuffer;
}
二:CVPixelBufferRef转换为CMSampleBufferRef:
// NV12数据转换为数据流
+ (CMSampleBufferRef)pixelBufferToSampleBuffer:(CVPixelBufferRef)pixelBuffer {
    CMSampleBufferRef sampleBuffer;
    CMTime frameTime = CMTimeMakeWithSeconds([[NSDate date] timeIntervalSince1970], 1000000000);
    CMSampleTimingInfo timing = {frameTime, frameTime, kCMTimeInvalid};
    CMVideoFormatDescriptionRef videoInfo = NULL;
    CMVideoFormatDescriptionCreateForImageBuffer(NULL, pixelBuffer, &videoInfo);
    
    OSStatus status = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, true, NULL, NULL, videoInfo, &timing, &sampleBuffer);
    if (status != noErr) {
        NSLog(@"Failed to create sample buffer with error %d.", (int)status);
    }
    CVPixelBufferRelease(pixelBuffer);
    if (videoInfo) {
        CFRelease(videoInfo);
    }
    return sampleBuffer;
}
三:对NV12裁剪代码2:

其实这个方法更多的是介绍怎么把i420进行裁剪。
我没有单独弄i420文件,这里直接先把NV12转换为i420,再进行裁剪

+ (CVPixelBufferRef)convertNV12ToI420ScreenshotsType1:(CMSampleBufferRef)sampleBufRef screenshotsFrame:(CGRect)screenshotsFrame {
    int screenshots_x = screenshotsFrame.origin.x;
    int screenshots_y = screenshotsFrame.origin.y;
    int screenshots_width = screenshotsFrame.size.width;
    int screenshots_hight = screenshotsFrame.size.height;
    // 确保宽高是偶数
    if (screenshots_width % 2 != 0) {
        screenshots_width++;
    }
    if (screenshots_hight % 2 != 0) {
        screenshots_hight++;
    }
    //CVPixelBufferRef是CVImageBufferRef的别名,两者操作几乎一致。
    //获取CMSampleBuffer的图像地址
    CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBufRef);
    if (!pixelBuffer) {
        return nil;
    }
    //表示开始操作数据
    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
    //图像宽度(像素)
    size_t buffer_width = CVPixelBufferGetWidth(pixelBuffer);
    //图像高度(像素)
    size_t buffer_height = CVPixelBufferGetHeight(pixelBuffer);
    //获取CVImageBufferRef中的y数据
    uint8_t *src_y_frame = (unsigned char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
    //获取CMVImageBufferRef中的uv数据
    uint8_t *src_uv_frame =(unsigned char *) CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
    //y stride
    size_t plane1_stride = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
    //uv stride
    size_t plane2_stride = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1);
    //y height
    size_t plane1_height = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0);
    //uv height
    size_t plane2_height = CVPixelBufferGetHeightOfPlane(pixelBuffer, 1);
    //y_size
    size_t plane1_size = plane1_stride * plane1_height;
    //uv_size
    size_t plane2_size = plane2_stride * plane2_height;
    //yuv_size(内存空间)
    size_t frame_size = plane1_size + plane2_size;
    size_t buffer_u_strate = plane2_stride / 2;
    size_t buffer_v_strate = plane2_stride / 2;
    
    // 截取区域不能超出原视频大小
    if (screenshots_x >= buffer_width ||
        screenshots_width > buffer_width ||
        screenshots_x + screenshots_width > buffer_width ||
        screenshots_y >= buffer_height ||
        screenshots_hight > buffer_height ||
        screenshots_y + screenshots_hight > buffer_height) {
        return nil;
    }

    // 1.NV12转换为I420
    uint8* buffer_frame = (unsigned char *)malloc(frame_size);
    uint8* buffer_u = buffer_frame + plane1_size;
    uint8* buffer_v = buffer_u + plane1_size / 4;

    libyuv::NV12ToI420(/*const uint8 *src_y*/ src_y_frame,
                       /*int src_stride_y*/ (int)plane1_stride,
                       /*const uint8 *src_uv*/ src_uv_frame,
                       /*int src_stride_uv*/ (int)plane2_stride,
                       /*uint8 *dst_y*/ buffer_frame,
                       /*int dst_stride_y*/ (int)plane1_stride,
                       /*uint8 *dst_u*/ buffer_u,
                       /*int dst_stride_u*/ (int)buffer_u_strate,
                       /*uint8 *dst_v*/ buffer_v,
                       /*int dst_stride_v*/ (int)buffer_v_strate,
                       /*int width*/ (int)buffer_width,
                       /*int height*/ (int)buffer_height);
    
    // 2.I420数据进行相应的裁剪
    // 步长必须是16的倍数,因为涉及到字节对齐,而且iOS13和之前的版本处理方式不一样,要注意
    int stride_length = 16;
    int scale_plane1_stride = screenshots_width;
    if ([UIDevice currentDevice].systemVersion.floatValue >= 13.0) {
        stride_length = 64;
    } else {
        stride_length = 16;
    }
    if ((screenshots_width % stride_length) != 0) {
        scale_plane1_stride = (screenshots_width / stride_length + 1) * stride_length;
    }
    
    int scale_plane2_stride = scale_plane1_stride;
    int scale_plane1_height = screenshots_hight;
    int scale_plane2_height = screenshots_hight / 2;
    int scale_plane1_size = scale_plane1_stride * scale_plane1_height;
    int scale_plane2_size = scale_plane2_stride * scale_plane2_height;
    int scale_frame_size = scale_plane1_size + scale_plane2_size;

    uint8* scale_buffer = (unsigned char *)malloc(scale_frame_size);
    uint8* scale_buffer_u = scale_buffer + scale_plane1_size;
    uint8* scale_buffer_v = scale_buffer_u + scale_plane1_size / 4;
    
    
    libyuv::ConvertToI420(/*const uint8 *src_frame*/ buffer_frame,
                          /*size_t src_size*/ frame_size,
                          /*uint8 *dst_y*/ scale_buffer,
                          /*int dst_stride_y*/ scale_plane1_stride,
                          /*uint8 *dst_u*/ scale_buffer_u,
                          /*int dst_stride_u*/ scale_plane1_stride >> 1,
                          /*uint8 *dst_v*/ scale_buffer_v,
                          /*int dst_stride_v*/ scale_plane1_stride >> 1,
                          /*int crop_x*/ screenshots_x,
                          /*int crop_y*/ screenshots_y,
                          /*int src_width*/ (int)plane1_stride,
                          /*int src_height*/ (int)buffer_height,
                          /*int crop_width*/ screenshots_width,
                          /*int crop_height*/ screenshots_hight,
                          /*enum RotationMode rotation*/ libyuv::kRotate0,
                          /*uint32 format*/ libyuv::FOURCC_I420);
    
    // 3.把缩放后的I420数据转换为NV12
    int nv12_plane1_stride = scale_plane1_stride;
    int nv12_width = screenshots_width;
    int nv12_hight = screenshots_hight;
    int nv12_frame_size = scale_frame_size;
    
    uint8 *nv12_dst_y = (uint8 *)malloc(nv12_frame_size);
    uint8 *nv12_dst_uv = nv12_dst_y + nv12_plane1_stride * nv12_hight;

    libyuv::I420ToNV12(/*const uint8 *src_y*/ scale_buffer,
                       /*int src_stride_y*/ scale_plane1_stride,
                       /*const uint8 *src_u*/ scale_buffer_u,
                       /*int src_stride_u*/ scale_plane1_stride >> 1,
                       /*const uint8 *src_v*/ scale_buffer_v,
                       /*int src_stride_v*/ scale_plane1_stride >> 1,
                       /*uint8 *dst_y*/ nv12_dst_y,
                       /*int dst_stride_y*/ nv12_plane1_stride,
                       /*uint8 *dst_uv*/ nv12_dst_uv,
                       /*int dst_stride_uv*/ nv12_plane1_stride,
                       /*int width*/ nv12_width,
                       /*int height*/ nv12_hight);
    
    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
    free(buffer_frame);
    free(scale_buffer);
    
    // 4.NV12转换为CVPixelBufferRef
    NSDictionary *pixelAttributes = @{(id)kCVPixelBufferIOSurfacePropertiesKey : @{}};
    CVPixelBufferRef dstPixelBuffer = NULL;
    CVReturn result = CVPixelBufferCreate(kCFAllocatorDefault,
                                          nv12_width, nv12_hight, kCVPixelFormatType_420YpCbCr8BiPlanarFullRange,
                                          (__bridge CFDictionaryRef)pixelAttributes, &dstPixelBuffer);

    CVPixelBufferLockBaseAddress(dstPixelBuffer, 0);
    uint8_t *yDstPlane = (uint8*)CVPixelBufferGetBaseAddressOfPlane(dstPixelBuffer, 0);
    memcpy(yDstPlane, nv12_dst_y, nv12_plane1_stride * nv12_hight);
    uint8_t *uvDstPlane = (uint8*)CVPixelBufferGetBaseAddressOfPlane(dstPixelBuffer, 1);
    memcpy(uvDstPlane, nv12_dst_uv, nv12_plane1_stride * nv12_hight / 2);
    if (result != kCVReturnSuccess) {
        NSLog(@"Unable to create cvpixelbuffer %d", result);
    }
    CVPixelBufferUnlockBaseAddress(dstPixelBuffer, 0);

    free(nv12_dst_y);

    return dstPixelBuffer;
}
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