RFC44：为ogrinfo和gdalinfo添加可解析的输出格式
作者：丹·达基·利特尔，法扎·马哈茂德
联系人：yahoo.com的danlittle，live.com的fazamhd
现状：发展。GDAL 2.0中实现的gdalinfo-json
总结
向ogrinfo和gdalinfo实用程序添加XML和JSON输出。
背景
ogrinfo和gdalinfo是非常有用的元数据收集工具。但是，它们基于文本的本地输出格式不容易被常见的外部工具解析。XML和JSON都很容易解析，添加这些输出格式将大大增加那些希望将ogrinfo和gdalinfo实用程序添加到脚本堆栈中的实用程序。
实施
在下面的github fork中可以看到一个示例实现 https://github.com/theduckylittle/gdal/blob/trunk/gdal/apps/ogrinfo.cpp
要将XML输出添加到每个实用程序中，需要将主循环“分解”为偶发块。还需要将所有诊断消息移动到STDERR，以确保STDOUT上的输出始终是可解析的。XML表示将使用内置于GDAL中的MiniXML库来构建。
为gdalinfo建议的json格式
{
"description": "...",
"driverShortName": "GTiff",
"driverLongName": "GeoTIFF",
"files": [ (if -nofl not specified)
"../gcore/data/byte.tif",
"../gcore/data/byte.tif.aux.xml"
],
"size": [
20,
20
],
"coordinateSystem": {
"proj": "+proj=.......", (if -proj4 specified)
"wkt": "PROJCS[....]"
},
"gcps": { (if -nogcp not specified)
"coordinateSystem": {
"proj": "+proj=.......", (if -proj4 specified)
"wkt": "PROJCS[....]"
},
"gcpList": [
{
"id": "1",
"info": "a",
"pixel": 0.5,
"line": 0.5,
"X": 0.0,
"Y": 0.0,
"Z": 0.0
},
{
"id": "2",
"info": "b",
.
.
.
}
]
},
"geoTransform": [
440720.000000000000000,
60.000000000000000,
0.0,
3751320.000000000000000,
0.0,
-60.000000000000000
],
"cornerCoordinates":{
"upperLeft":[
440720.0,
3751320.0
],
"lowerLeft":[
440720.0,
3750120.0
],
"upperRight":[
441920.0,
3751320.0
],
"lowerRight":[
441920.0,
3750120.0
],
"center":[
441320.0,
3750720.0
]
},
"wgs84Extent":{
"type":"Polygon",
"coordinates":[
[
[
-117.642054,
33.9023677
],
[
-117.6419729,
33.8915454
],
[
-117.6290752,
33.9024346
],
[
-117.6289957,
33.8916123
],
[
-117.642054,
33.9023677
]
]
]
},
"rat": { (if -norat not specified)
"row0Min": 40918,
"binSize": 1,
"fieldDefn": [
{
"index": 0,
"name": "Histogram",
"type": "integer",
"usage": "PixelCount"
},
{
"index": 1,
"name": "fieldName2",
"type": 2,
"usage": 2
},
],
"rows": [
{
"index": 0,
"f": [
1,
4
]
},
{
"index": 1,
"f": [
5,
4
]
},
.
.
.
]
},
"metadata": { (if -nomd not specified)
"": {
"key1": "value1"
},
"IMAGE_STRUCTURE": {
"key1": "value1"
},
"OTHER_DOMAIN": {
"key1": "value1"
},
},
"cornerCoordinates": {
"upperLeft": [
440720.000,
3751320.000
],
"lowerLeft": [
440720.000,
3750120.000
],
"upperRight": [
441920.000,
3751320.000
],
"lowerRight": [
441920.000,
3750120.000
],
"center": [
441320.000,
3750720.000
]
},
"bands": [
{
"description": "...",
"band": 1,
"block": [
20,
20
],
"type": "Byte",
"colorInterp": "Gray",
"min": 74.000,
"max": 255.000,
"computedMin": 74.000, (if -mm specified)
"computedMax": 255.000,
"minimum": 74.000, (if -stats specified)
"maximum": 255.000,
"mean": 126.765,
"stdDev": 22.928,
"unit": "....",
"offset": X,
"scale": X,
"noDataValue": X,
"overviews": [
{
"size": [
400,
400 ],
"checksum": X (if -checksum specified)
},
{
"size": [
200,
200 ],
"checksum": X (if -checksum specified)
}
],
"mask": {
"flags": [
"PER_DATASET",
"ALPHA"
],
"overviews": [
{
"size": [
400,
400 ]
},
{
"size": [
200,
200 ],
}
]
},
"metadata": { (if -nomd not specified)
"__default__": {
"key1": "value1"
},
"IMAGE_STRUCTURE": {
"key1": "value1"
},
"OTHER_DOMAIN": {
"key1": "value1"
},
},
"histogram": { (if -hist specified)
"count": 25,
"min": -0.5,
"max": 255.5,
"buckets": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
},
"checksum": 4672, (if -checksum specified)
"colorTable": { (if -noct not specified)
"palette": "RGB",
"count": 6,
"entries": [
[255,255,255,255],
[255,255,208,255],
[255,255,204,255],
[153,204,255,255],
[0,153,255,255],
[102,102,102,255]
]
}
},
{
"band": 2,
"block": [
20,
20
],
.
.
.
}
]
}
受影响的驱动程序
没有。
受影响的公用事业
gdalinfo
添加“-xml”输出选项。
添加“-json”输出选项。
ogrinfo
添加“-xml”输出选项。
添加“-json”输出选项。
向后兼容性
这种变化对C API／ABI和C++ +API/ABI级别的向后兼容性没有影响。默认输出将保持不变。新的XML输出将只影响在命令行上指定“-XML”或“-json”的用户。
测试
Python自动测试套件将被扩展以测试新的XML/JSON输出，现有的测试将被修改以检查STDERR的诊断消息。
车票
没有票。
投票历史
提出。