QT uses ffmpeg4 to convert the qimage of ARGB to yuv422p

Preface

 use FFmpeg4 Implement a very simple argb transformation yuv422p Function of 

1. adopt QPixmap obtain QLabel Display the interface and turn to image, Pass in the conversion function

QPixmap pixmap(subtitleLabel->size());
pixmap.fill(Qt::transparent);// Set up pixmap The background is transparent 
subtitleLabel->render(&pixmap);
QImage image = pixmap.toImage();
unsigned char *imgBuf = image.bits();
argbToyuv(image.width(),image.height(),imgBuf);

2. establish rgbBuffer And fill in image Of rgbBuf data , establish yuvBuffer, establish SwsContext Conversion context , Use sws_scale convert

#define HI_ALIGN_UP(x, a) ( ( ((x) + ((a) - 1) ) / (a) ) * (a) )
int argbToyuv(int width, int height, unsigned char *rgbBuf)
{
    
    int ret, numBytes = 0;
    uint8_t *src_data[4], *dst_data[4];
    int src_linesize[4], dst_linesize[4];
    int src_w = width, src_h = height, dst_w, dst_h;
    dst_w = HI_ALIGN_UP(src_w, 16);// Pixel alignment 
    dst_h = HI_ALIGN_UP(src_h, 16);
    enum AVPixelFormat src_pix_fmt = AV_PIX_FMT_ARGB, dst_pix_fmt = AV_PIX_FMT_YUV422P;
    SwsContext *sws_ctx = NULL;

	/* create argbBuffer  Before creating conversion , fill image Data buffer*/
    numBytes = av_image_get_buffer_size(src_pix_fmt, src_w, src_h, 1);//1920*1080*4
    uint8_t *argbBuffer = NULL;
    (uint8_t*)av_malloc(numBytes*sizeof(uint8_t));
    av_image_fill_arrays(src_data, src_linesize, argbBuffer, src_pix_fmt, src_w, src_h, 1);
    src_data[0] = rgbBuf;
    src_data[1] = src_data[0]+(width*height);
    src_data[2] = src_data[1]+(width*2*height);

// FILE *output_rgb=fopen("/opt/vw30/bin/subtitle_rgb","ab+");
// fwrite(rgbBuf,(src_w*src_h)*3,1,output_rgb);
// fclose(output_rgb);

	/* create yuvBuffer  Create the received after conversion buffer*/
    numBytes = av_image_get_buffer_size(dst_pix_fmt, dst_w, dst_h, 1);
    uint8_t *yuvBuffer = NULL;
    yuvBuffer = (uint8_t*)av_malloc(numBytes*sizeof(uint8_t));
    av_image_fill_arrays(dst_data, dst_linesize, yuvBuffer ,dst_pix_fmt, dst_w, dst_h, 1);

    /* create scaling context  Create transformation context */
    sws_ctx = sws_getContext(src_w, src_h, src_pix_fmt,
                             dst_w, dst_h, dst_pix_fmt,
                             SWS_BILINEAR, NULL, NULL, NULL);
    if (!sws_ctx) {
    
        fprintf(stderr,
                "Impossible to create scale context for the conversion "
                "fmt:%s s:%dx%d -> fmt:%s s:%dx%d\n",
                av_get_pix_fmt_name(src_pix_fmt), src_w, src_h,
                av_get_pix_fmt_name(dst_pix_fmt), dst_w, dst_h);
        ret = AVERROR(EINVAL);
        goto end;
    }
    /*sws_scale  Conversion function */
    ret = sws_scale(sws_ctx, src_data, src_linesize, 0, src_h, dst_data, dst_linesize);
    if (ret < 0){
    
        qDebug()<<"sws_scale error";
        goto end;
    }

end:
    if(yuvBuffer){
    
        av_free(yuvBuffer);
    }
    if(argbBuffer){
    
       av_free(argbBuffer);
    }
    if(sws_ctx){
    
       sws_freeContext(sws_ctx);
    }

// FILE *output=fopen("/opt/vw30/bin/subtitle.yuv","ab+");
// fwrite(dst_data[0],dst_w*dst_h,1,output);
// fwrite(dst_data[1],dst_w*dst_h/4,1,output);
// fwrite(dst_data[2],dst_w*dst_h/4,1,output);
    return 0;
}