R栅格在绘图时避免使用空白区域

本文介绍了R栅格在绘图时避免使用空白区域的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一张图片，我想在0,0左右底角只绘制100 * 100平方。当我使用下面的命令时。为什么我的裁剪图像周围会出现白色空间？ 如何避免它并确保我得到准确的100 * 100图像？

I have an image and i want to plot only 100*100 square with left hand bottom corner at 0,0. when i use below commands. Why do i get a white space around my cropped image? how can i avoid it and ensure that I get exact 100*100 image?

如果你想重复我的例子，你可以在线使用任何图像1（假设图像大于100 * 100像素）

If you want to repeat my example, you can use any image on line 1 (provided that the image is bigger than 100*100 pixels)

r <- raster("C:/Users/nnnn/Desktop/geo.jpg") vector= getValues(r) plot(r) r par(mar=c(0,0,0,0)) par(oma=c(0,0,0,0)) par(mai=c(0,0,0,0)) par(omi=c(0,0,0,0)) plot(r,xlim=c(0,100),ylim=c(0,100),legend=FALSE,axes=FALSE)

推荐答案

这是我的最佳镜头：

library(raster) ## An example raster logo <- raster(system.file("external/rlogo.grd", package="raster")) ## Clip out the lower-left 50*100 pixel rectangle as a new raster 'r' cropWithRowCol <- function(r, rows, cols) { cc <- cellFromRowColCombine(r, rownr=rows, colnr=cols) crop(r, rasterFromCells(r, cc, values=FALSE)) } r <- cropWithRowCol(logo, nrow(logo) - 49:0, 1:100) ## Extract multipliers used to appropriately size the selected device w <- ncol(r)/max(dim(r)) h <- nrow(r)/max(dim(r)) ## Set up appropriately sized device with no borders and required coordinate system ## png("eg.png", width=480*w, height=480*h) dev.new(width=5*w, height=5*h) plot.new() par(mar=c(0,0,0,0), oma=c(0,0,0,0)) plot.window(xlim=extent(r)[1:2], ylim=extent(r)[3:4], xaxs="i",yaxs="i") ## Finally, plot the (sub-)raster to it plot(r, axes=FALSE, legend=FALSE, add=TRUE) ## dev.off()

（请记住，在交互式可调整大小的设备中，更改设备的大小会使绘制的地图的宽高比变得混乱。）

(Please remember that, in an interactively resizable device, changing the device's size will mess up the plotted map's aspect ratio.)