从网站加载图片 [英] Load image from website

问题描述

我正在尝试向我创建的一些地块添加一些化学结构图像。我正在使用ACToR数据库来访问化学结构。例如：

（ http：//演员.epa.gov / actor / image？format = png％3Aw250％2Ch250& casrn = 80-05-7 ）

这个网站的好东西你可以改变url中的大小和化学物质，所以我可以自动抓取图像。我希望存储一个包含CAS号码的对象，然后遍历CAS号码进行绘图。

例如：

  library（png）
 casnums < - （80-05-7，77-40-7，1478-61-1）
 image.list < -  list（）
 for（cas in casnums）{
 image.list [[cas]]<  -  readPNG（paste0（http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=，cas ））
} 
  

我尝试使用 readPNG code> png 包，并尝试使用 rgdal 包。不幸的是，据我所知，ACToR只会以png或jpeg格式生成图像，所以我不能使用 grImport 包来读取矢量图像。

我真的希望找到一个解决方案，我不必手动下载每个图像 - 其中有很多。我会打开一个解决方案，其中R将图像下载到一个文件夹，然后我可以使用类似于 png 包或 rgdal 包装以加载图像并绘制它们。

回覆@ialm：这是我第一次评论后尝试的：

 > download.file（url =http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7，destfile =test.png）
尝试URL'http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7'
内容类型'image / png'长度200字节
打开URL 
下载6691字节
 
警告消息：
在download.file（url =http://actor.epa.gov/actor/image?format=png ％3Aw250％2Ch250& casrn = 80-05-7，
下载长度6691！=报告长度200 
  

当我打开图像时，它只有7 KB，并且在图像查看器中得到以下消息：Windows Photo Viewer无法打开此图像，因为该文件似乎已损坏，损坏或太大了。

我应该注意到，我是（反对我的意愿）使用Windows 7.我也尝试使用RStudio和R. RStudio给了我警告消息，R没有 - 但是R创建了似乎是同一个文件（7KB），但仍然没有打开。

为了回应@Greg Snow：只是为了添加一些上下文，我在RStudio的一个新的R控制台中运行以下操作。我使用64位Rv3.0.1和64位RStudio v0.97.551。

 >图书馆（png）
> search（）
 [1].GlobalEnvpackage：pngtools：rstudiopackage：statspackage：graphicspackage：grDevices
 [7]package：utils package：datasetspackage：methodsAutoloadspackage：base
> con<  -  url（http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=1478-61-1，open ='rb'）
> rawpng<  -  readBin（con，what ='raw'，n = 1e6）
>关闭（con）
> png1<  -  readPNG（rawpng）
 readPNG（rawpng）中的错误：libpng错误：错误的自适应过滤器值
> ls（）
 [1]conrawpng
  

解决方案

这是一个可以为单个图像工作的方法（可以将其包含在循环中使用的函数中）：

  con<  -  url（http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=1478-61-1，
 open ='rb'）
 
 rawpng<  -  readBin（con，what ='raw'，n = 50000）
 
 close（con）
 
 png1<  -  readPNG（rawpng）
  

我使用以下方式进行了测试：

  plot（1:10，type ='n'）
 rasterImage（as.raster（png1），3,3,8,8） 
  

花了一些猜测来获得50000，而对于其他文件可能会有所不同（实际上我应该使用48849，但是真的很可能会在文件之间改变）。

I am trying to add some chemical structure images to some plots I have created. I am using the ACToR database to access the chemical structures. For example:

(http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7)

The nice thing about this site is you can change the size and the chemical within the url, so I can automate grabbing the images. My hope was to store an object containing CAS numbers, then iterate through the CAS numbers to make the plots.

For example:

library(png)
casnums <- ("80-05-7","77-40-7","1478-61-1")
image.list <- list()
for(cas in casnums){
  image.list[[cas]] <- readPNG(paste0("http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=",cas))
}

I have tried using readPNG from the png package, and tried to use the rgdal package as well. Unfortunately, as far as I can tell, ACToR will only generate the images in a png or jpeg format - so I cannot use the grImport package for reading vector images.

I am really hoping to find a solution where I do not have to manually download each image - there are a lot of them. I would be open to a solution where R goes and dowloads the images to a folder, then I could use something like the png package, or the rgdal package to load the image and plot them.

In response to @ialm: Here is what I tried after your first comment:

> download.file(url="http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7",destfile="test.png")
trying URL 'http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7'
Content type 'image/png' length 200 bytes
opened URL
downloaded 6691 bytes

Warning message:
In download.file(url = "http://actor.epa.gov/actor/image?format=png%3Aw250%2Ch250&casrn=80-05-7",  :
  downloaded length 6691 != reported length 200

When I go to open the image it is only 7 KB and I get the follow message in the image viewer: "Windows Photo Viewer can't open this picture because the file appears to be damaged, corrupted, or is too large."

I should note that I am (against my will) using Windows 7. I also tried using both RStudio, and R. RStudio gave me the warning message, and R did not - but R created what appears to be the same file (7KB) and still does not open.

In response to @Greg Snow: Just to add some context, I ran the following from a fresh R Console in RStudio. I used 64 bit Rv3.0.1 and 64-bit RStudio v0.97.551.

> library(png)
> search()
 [1] ".GlobalEnv"        "package:png"       "tools:rstudio"     "package:stats"     "package:graphics"  "package:grDevices"
 [7] "package:utils"     "package:datasets"  "package:methods"   "Autoloads"         "package:base"     
> con <- url("http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=1478-61-1",open='rb')
> rawpng <- readBin(con, what='raw', n=1e6)
> close(con)
> png1 <- readPNG(rawpng)
Error in readPNG(rawpng) : libpng error: bad adaptive filter value
> ls()
[1] "con"    "rawpng"

解决方案

Here is an approach that worked for me for a single image (it could be wrapped in a function to be used in the loop):

con <- url("http://actor.epa.gov/actor/image?format=png%3Aw1000%2Ch1000&casrn=1478-61-1",
    open='rb')

rawpng <- readBin(con, what='raw', n=50000)

close(con)

png1 <- readPNG(rawpng)

I tested it using:

plot(1:10, type='n')
rasterImage( as.raster(png1), 3,3,8,8 )

It took some guesswork to get the 50000 and that may be different for other files (actually I should have used 48849, but then it really would be likely to change between files).

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