[英]How to get RGB raster image with UTM coordinates
I have a three layer raster with red, green, and blue channel values in it. 我有一个三层栅格,其中有红色,绿色和蓝色通道值。 I can plot the image with raster::plotRGB
, but I need to add axes with UTM coordinates. 我可以使用raster::plotRGB
绘制图像,但是我需要添加具有UTM坐标的轴。 Coordinates can be added with axes=TRUE
, but they are floating in space and look bad. 可以使用axes=TRUE
添加axes=TRUE
,但是axes=TRUE
在空间中浮动并且看上去很差。 I would like to get the coordinates as they show up in plots created with the raster
plot
method, or better yet as they appear when using rasterVis::levelplot
. 我想获得坐标显示在使用raster
plot
方法创建的plot
的坐标,或者更好的是使用rasterVis::levelplot
时显示的rasterVis::levelplot
。
Ultimately, I need to create a raster image with UTM coordinates, a scale bar, and north arrow. 最终,我需要创建一个具有UTM坐标,比例尺和向北箭头的栅格图像。 This needs to be done using the plotRGB
function in the raster
package of R, or something with a similar functionality, as I need to assign the colour of each pixel by hand (no colour ramps). 这需要使用R的raster
包中的plotRGB
函数或具有类似功能的东西来完成,因为我需要手动分配每个像素的颜色(无色带)。
This is an ancient post, but it's a good question so I'll give it an answer. 这是一篇古老的文章,但这是一个好问题,所以我给它一个答案。
I'll give an example of how this might be done with rasterVis::levelplot
, using the 3-channel R logo raster data that comes with raster
. 我给这如何可能会做一个例子rasterVis::levelplot
,使用自带的3槽R标志栅格数据raster
。
library(rasterVis)
b <- brick(system.file("external/rlogo.grd", package="raster"))
Create an empty raster
with the same dimensions and extent as the brick. 创建一个具有与砖相同尺寸和范围的空raster
。
r <- raster(b)
Calculate the hexadecimal colours corresponding to the values of the RGB channels, and coerce to factor
. 计算与RGB通道的值相对应的十六进制颜色,并强制转换为factor
。
cols <- factor(rgb(b[], maxColorValue=255))
Assign these factor values to the raster's cells. 将这些因子值分配给栅格像元。
r[] <- cols
Plot with levelplot
, extracting the hexadecimal colours from the levels of cols
and passing them to col.regions
. 使用levelplot
,从cols
的水平中提取十六进制颜色并将其传递到col.regions
。
levelplot(r, col.regions=as.character(levels(cols)), colorkey=FALSE)
For the north arrow and the scale bar, we will look to @OscarPerpiñán's docs . 对于北箭头和比例尺,我们将查看@OscarPerpiñán的docs 。
levelplot(r, col.regions=as.character(levels(cols)), colorkey=FALSE) +
layer(SpatialPolygonsRescale(layout.north.arrow(), offset = c(5, 10), scale = 10)) +
layer({
xs <- seq(5, 25, by=5)
grid.rect(x=xs, y=5,
width=5, height=2,
gp=gpar(fill=rep(c('transparent', 'black'), 2)),
default.units='native')
grid.text(x=xs-2.5, y=8, seq(0, 400, by=100),
gp=gpar(cex=0.7),
default.units='native')
})
I'll leave it up to you to calculate the true distance (passed to grid.text
) associated with the width, in map units, of the rectangles. 我grid.text
您自己来计算与矩形的宽度(以地图单位为单位)关联的真实距离(传递给grid.text
)。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.