Question

今天我偶然发现了（对我而言）奇怪的事情，即当我运行此代码时

asset_idx01

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n asset_idx01 -z spotlight-prod-cluster01 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c asset_indexconfig.xml -cp lily.zk=spotlight-prod-cluster01

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n asset_idx01 --batch BUILD_REQUESTED

asset_idx02

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n asset_idx02 -z spotlight-prod-cluster02 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster02:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c asset_indexconfig.xml -cp lily.zk=spotlight-prod-cluster02

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n asset_idx02 --batch BUILD_REQUESTED

brightcove_idx01

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n brightcove_idx01 -z spotlight-prod-cluster01 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c brightcove_indexconfig.xml -cp lily.zk=spotlight-prod-cluster01

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n brightcove_idx01 --batch BUILD_REQUESTED 

brightcove_idx02

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n brightcove_idx02 -z spotlight-prod-cluster02 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster02:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c brightcove_indexconfig.xml -cp lily.zk=spotlight-prod-cluster02

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n brightcove_idx02 --batch BUILD_REQUESTED 

fortune_idx01

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n fortune_idx01 -z spotlight-prod-cluster01 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c fortune_indexconfig.xml -cp lily.zk=spotlight-prod-cluster01

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n fortune_idx01 --batch BUILD_REQUESTED

fortune_idx02

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n fortune_idx01 -z spotlight-prod-cluster02 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster02:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c fortune_indexconfig.xml -cp lily.zk=spotlight-prod-cluster02

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n fortune_idx02 --batch BUILD_REQUESTED

populist_idx01

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n populist_idx01 -z spotlight-prod-cluster01 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c indexconfig.xml -cp lily.zk=spotlight-prod-cluster01

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n populist_idx01 --batch BUILD_REQUESTED

populist_idx02

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n populist_idx02 -z spotlight-prod-cluster02 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c indexconfig.xml -cp lily.zk=spotlight-prod-cluster02

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n populist_idx02 --batch BUILD_REQUESTED

twitter_stat_idx01

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n twitter_stats_idx01 -z spotlight-prod-cluster01 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster01:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c twitter_stats_indexconfig.xml -cp lily.zk=spotlight-prod-cluster01

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n twitter_stats_idx01 --batch BUILD_REQUESTED

twitter_stat_idx02

/usr/lib/hbase-indexer/bin/hbase-indexer add-indexer -n twitter_stats_idx02 -z spotlight-prod-cluster02 -cp solr.mode=classic -cp solr.shard.1=http://spotlight-prod-cluster02:7575/solr -r org.lilyproject.indexer.hbase.mapper.LilyIndexerComponentFactory -cp solr.sharder=org.lilyproject.indexer.hbase.mapper.LilySharder -c twitter_stats_indexconfig.xml -cp lily.zk=spotlight-prod-cluster02

/usr/lib/hbase-indexer/bin/hbase-indexer update-indexer -n twitter_stats_idx02 --batch BUILD_REQUESTED

我得到的输出看起来像这样：

int i,j;
uint8_t* p = y.data;
for( i = 0; i < y.rows; ++i)
{
    for ( j = 0; j < y.cols; ++j)
    {
       std::cout << y.at<double>(i,j) << std::endl;
       std::cout << saturate_cast<double>(p[i*y.cols + j]) << std::endl;
    }
}

有人可以向我解释为什么会这样吗？

不应该一样吗？

Answer 1

p指向的内存是：

// |251 |123 |63  |254 |...   uint8_t
// +----+----+----+----+----+
// | FB | 7B | 3F | FE |... | hex
// +----+----+----+----+----+
// |0.00683212          ...   double

当你执行y.at<double>(i,j)时，基本上是：

p[i*y.cols + j]

您正在以uint8_t的形式访问数组，因此转换为uint8_t的{{1}}保持相同的值。当您通过double访问它时，它会将其作为.at<double>()

进行访问

访问Mat的每个像素

1 个答案: