ExportToPNG (arcpy.mapping)

摘要

Exports the page layout or data frame of a map document (.mxd) to the Portable Network Graphics (PNG) format.

讨论

PNG is a raster format designed for use on the Web as an alternative to GIF. It supports 24-bit color and is compressed using a lossless compression. PNG files also have the ability to define a transparent color; part of the image can display as transparent in a Web browser, allowing backgrounds, images, or colors to show through. On most images, PNG can achieve greater compression (and thus smaller file sizes) than GIF. PNGs exported from the data view in ArcMap can be generated with an accompanying world file for use as georeferenced raster data. This format is gaining popularity in the Web design community.

要导出单个数据框（而不是整个页面布局），可将 DataFrame 对象传给函数的 data_frame 参数。由于数据框导出不具有可提供高度和宽度信息的关联页面，所以必须通过 df_export_width 和 df_export_height 参数来提供此信息。

对于页面布局导出和数据框导出，控制生成图像图形质量的方式有所不同。导出页面布局时，通过更改 resolution 参数来控制图像细节。导出数据框时，保持 resolution 参数的默认值，更改 df_export_width 和 df_export_height 参数来更改图像细节。高度和宽度参数直接控制在导出文件中生成的像素数，且仅在导出数据框时使用。像素数较高的图像具有较高的图像细节。对于大多数页面布局导出，默认参数值应在第一次尝试时生成良好的结果和美观的导出图像。对于数据框导出，您可能需要对 df_export_width 和 df_export_height 值进行若干次试验，之后才能得到理想的结果。

World files are not generated for page layouts; a referenced data frame must be provided or the export will fail.

Refer to the Exporting your map topic in ArcGIS Help for more detailed discussions on exporting maps.

语法

ExportToPNG (map_document, out_png, {data_frame}, {df_export_width}, {df_export_height}, {resolution}, {world_file}, {color_mode}, {background_color}, {transparent_color}, {interlaced})

参数	说明	数据类型
map_document	A variable that references a MapDocument object.	MapDocument
out_png	A string that represents the path and file name for the output export file.	String
data_frame	A variable that references a DataFrame object. Use the string/constant "PAGE_LAYOUT" to export the map document's page layout instead of an individual data frame. (默认值为 PAGE_LAYOUT)	Object
df_export_width	A number that defines the width of the export image in pixels for a data frame export. df_export_width is only used when exporting a data frame. Exporting a page layout uses the map document page width instead of df_export_width. (默认值为 640)	Integer
df_export_height	A number that defines the height of the export image in pixels for a data frame export. df_export_height is only used when exporting a data frame. Exporting a page layout uses the map document page height instead of df_export_height. (默认值为 480)	Integer
resolution	A number that defines the resolution of the export file in dots per inch (DPI). (默认值为 96)	Integer
world_file	If set to True, a georeferenced world file is created. The file contains pixel scale information and real-world coordinate information. (默认值为 False)	Boolean
color_mode	This value specifies the number of bits used to describe color. 24-BIT_TRUE_COLOR —24-bit true color 8-BIT_PALETTE —8-bit palette 8-BIT_GRAYSCALE —8-bit grayscale 1-BIT_MONOCHROME_MASK —1-bit monochrome mask 1-BIT_MONOCHROME_THRESHOLD —1-bit monochrome threshold (默认值为 24-BIT_TRUE_COLOR)	String
background_color	A defined color is used as a background to the image, or as a mask in the case of monochrome masked exports. (默认值为 255, 255, 255)	String
transparent_color	A defined color to be displayed as transparent in the image.	String
interlaced	If set to True, an interlaced image will be created. An interlaced image displays as a series of scan lines rather than as a whole image at one time. (默认值为 False)	Boolean

代码实例

ExportToPNG example 1

This script opens a map document and exports the page layout to a PNG file using default values for all options.

import arcpy
mxd = arcpy.mapping.MapDocument(r"C:\Project\Project.mxd")
arcpy.mapping.ExportToPNG(mxd, r"C:\Project\Output\Project.png")
del mxd

ExportToPNG example 2

This script will export a single data frame instead of the entire page layout, similar to exporting from data view in the ArcMap application. The default values for df_export_width and df_export_height are 640 and 480. By passing larger values for these parameters, we are able to produce an output image with higher detail. Setting world_file = True generates a georeferenced world file in the same directory as the output file.

import arcpy
mxd = arcpy.mapping.MapDocument(r"C:\Project\Project.mxd")
df = arcpy.mapping.ListDataFrames(mxd, "Transportation")[0]
arcpy.mapping.ExportToPNG(mxd, r"C:\Project\Output\ProjectDataFrame.png", df,
                          df_export_width=1600,
                          df_export_height=1200,
                          world_file=True)
del mxd