android实现将位置信息写入JPEG图片文件
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2023-11-27 08:52:28
通过exifinterface可以将拍照时的一些属性信息写入图片文件里,其中包括经纬度信息。本文介绍一种将经纬度坐标写入jpeg图片文件的方法!
核心代码
/*...
通过exifinterface可以将拍照时的一些属性信息写入图片文件里,其中包括经纬度信息。本文介绍一种将经纬度坐标写入jpeg图片文件的方法!
核心代码
/** * 浮点型经纬度值转成度分秒格式 * * @param coord * @return */ public string decimaltodms(double coord) { string output, degrees, minutes, seconds; // gets the modulus the coordinate divided by one (mod1). // in other words gets all the numbers after the decimal point. // e.g. mod := -79.982195 % 1 == 0.982195 // // next get the integer part of the coord. on other words the whole // number part. // e.g. intpart := -79 double mod = coord % 1; int intpart = (int) coord; // set degrees to the value of intpart // e.g. degrees := "-79" degrees = string.valueof(intpart); // next times the mod1 of degrees by 60 so we can find the integer part // for minutes. // get the mod1 of the new coord to find the numbers after the decimal // point. // e.g. coord := 0.982195 * 60 == 58.9317 // mod := 58.9317 % 1 == 0.9317 // // next get the value of the integer part of the coord. // e.g. intpart := 58 coord = mod * 60; mod = coord % 1; intpart = (int) coord; if (intpart < 0) { // convert number to positive if it's negative. intpart *= -1; } // set minutes to the value of intpart. // e.g. minutes = "58" minutes = string.valueof(intpart); // do the same again for minutes // e.g. coord := 0.9317 * 60 == 55.902 // e.g. intpart := 55 coord = mod * 60; intpart = (int) coord; if (intpart < 0) { // convert number to positive if it's negative. intpart *= -1; } // set seconds to the value of intpart. // e.g. seconds = "55" seconds = string.valueof(intpart); // i used this format for android but you can change it // to return in whatever format you like // e.g. output = "-79/1,58/1,56/1" output = degrees + "/1," + minutes + "/1," + seconds + "/1"; // standard output of d°m′s″ // output = degrees + "°" + minutes + "'" + seconds + "\""; return output; } /** * 将经纬度信息写入jpeg图片文件里 * * @param picpath * jpeg图片文件路径 * @param dlat * 纬度 * @param dlon * 经度 */ public void writelatlonintojpeg(string picpath, double dlat, double dlon) { file file = new file(picpath); if (file.exists()) { try { exifinterface exif = new exifinterface(picpath); string taglat = exif .getattribute(exifinterface.tag_gps_latitude); string taglon = exif .getattribute(exifinterface.tag_gps_longitude); if (taglat == null && taglon == null) // 无经纬度信息 { exif.setattribute(exifinterface.tag_gps_latitude, decimaltodms(dlat)); exif.setattribute(exifinterface.tag_gps_latitude_ref, dlat > 0 ? "n" : "s"); // 区分南北半球 exif.setattribute(exifinterface.tag_gps_longitude, decimaltodms(dlon)); exif.setattribute(exifinterface.tag_gps_longitude_ref, dlon > 0 ? "e" : "w"); // 区分东经西经 exif.saveattributes(); } } catch (exception e) { } } }
测试代码
string strimgpath = getimagecachepath() + file.separator + "1.jpg"; exifinterface eif = new exifinterface(strimgpath); string lat = eif.getattribute(exifinterface.tag_gps_latitude); string latref = eif.getattribute(exifinterface.tag_gps_latitude_ref); string lon = eif.getattribute(exifinterface.tag_gps_longitude); string lonref = eif.getattribute(exifinterface.tag_gps_longitude_ref); system.out.println("latitude ref - " + latref); system.out.println("latitude - " + lat); system.out.println("longitude ref - " + lonref); system.out.println("longitude - " + lon); if (lat == null && lon == null) // 没有位置信息才写入 { writelatlonintojpeg(strimgpath, 39.23456, 116.123456); }
第一次运行结果
05-22 17:36:24.566: i/system.out(17966): latitude ref - null 05-22 17:36:24.566: i/system.out(17966): latitude - null 05-22 17:36:24.566: i/system.out(17966): longitude ref - null 05-22 17:36:24.566: i/system.out(17966): longitude - null
原始图片没有位置信息,通过调用writelatlonintojpeg(strimgpath, 39.23456, 116.123456)来模拟写入一个位置。
第二次运行结果
05-22 17:37:11.446: i/system.out(17966): latitude ref - n 05-22 17:37:11.446: i/system.out(17966): latitude - 39/1,14/1,4/1 05-22 17:37:11.446: i/system.out(17966): longitude ref - e 05-22 17:37:11.446: i/system.out(17966): longitude - 116/1,7/1,24/1
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