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  • My Unicomp Model M is double-striking on a key. What to do?

    - by Alex
    I realize this isn't strictly a computer-related question, but I figured that if there's any place to go for help about a broken keyboard, it would be a power users' forum. The O key on my Unicomp Model M has the tendency to strike twice. In other words, I press the key once, and it sends out two letters. There is probably a mechanical solution to this, but I'm not familiar enough with how these things work to come up with a fix myself. Has anyone had this problem?

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  • Double GPRS/EDGE speed with two mobile phones at once?

    - by Patrick
    Hi, I'm using my mobile phone to connect to the internet in an area where only GPRS/EDGE is available. To increase the connection speed I would like to use a technique called connection teaming. E.g. I would use two mobile phones / usb sticks to go online with different providers at the same time and let the software distribute requests over both connections. My questions are: is there a software available to do connection teaming? It sounds like Midpoint was able to do it but it's over 7 years old and is unlikely to run on Windows 7 has anybody tried this? Thanks a lot, Patrick

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  • Can a Double-Density Floppy drive be swapped out for a High-Density drive?

    - by Ben
    I'm trying to fix the floppy drive in my Roland MC-500. The floppy drive inside is a Matsushita DDF3-1 which doesn't seem to be in production anymore. The DDF3-2 is still available, however it is an HD drive. Does anyone know off the top of their heads if there is any issue with simply swapping the two drives? Could the power usage be different on the drives? Since the machine is expecting a 720k DD drive, are there any jumper settings to have the HD drive function as a DD drive?

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  • The internal storage of a DATETIMEOFFSET value

    - by Peter Larsson
    Today I went for investigating the internal storage of DATETIME2 datatype. What I found out was that for a datetime2 value with precision 0 (seconds only), SQL Server need 6 bytes to represent the value, but stores 7 bytes. This is because SQL Server add one byte that holds the precision for the datetime2 value. Start with this very simple repro declare    @now datetimeoffset(7) = '2010-12-15 21:04:03.6934231 +03:30'   select     cast(cast(@now as datetimeoffset(0)) as binary(9)),            cast(cast(@now as datetimeoffset(1)) as binary(9)),            cast(cast(@now as datetimeoffset(2)) as binary(9)),            cast(cast(@now as datetimeoffset(3)) as binary(10)),            cast(cast(@now as datetimeoffset(4)) as binary(10)),            cast(cast(@now as datetimeoffset(5)) as binary(11)),            cast(cast(@now as datetimeoffset(6)) as binary(11)),            cast(cast(@now as datetimeoffset(7)) as binary(11)) Now we are going to copy and paste these binary values and investigate which value is representing what time part. Prefix  Ticks       Ticks         Days    Days    Suffix  Suffix  Original value ------  ----------  ------------  ------  ------  ------  ------  ------------------------ 0x  00  0CF700             63244  A8330B  734120  D200       210  0x000CF700A8330BD200 0x  01  75A609            632437  A8330B  734120  D200       210 0x0175A609A8330BD200 0x  02  918060           6324369  A8330B  734120  D200       210  0x02918060A8330BD200 0x  03  AD05C503        63243693  A8330B  734120  D200       210  0x03AD05C503A8330BD200 0x  04  C638B225       632502470  A8330B  734120  D200       210  0x04C638B225A8330BD200 0x  05  BE37F67801    6324369342  A8330B  734120  D200       210  0x05BE37F67801A8330BD200 0x  06  6F2D9EB90E   63243693423  A8330B  734120  D200       210  0x066F2D9EB90EA8330BD200 0x  07  57C62D4093  632436934231  A8330B  734120  D200       210  0x0757C62D4093A8330BD200 Let us use the following color schema Red - Prefix Green - Time part Blue - Day part Purple - UTC offset What you can see is that the date part is equal in all cases, which makes sense since the precision doesn't affect the datepart. If you add 63244 seconds to midnight, you get 17:34:04, which is the correct UTC time. So what is stored is the UTC time and the local time can be found by adding "utc offset" minutes. And if you look at it, it makes perfect sense that each following value is 10 times greater when the precision is increased one step too. //Peter

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  • DIMMs: Single vs. Double vs. Quad Rank

    - by MikeyB
    What difference does the 'Rank' of DIMMs make to server memory? For example, when looking at server configurations I see the following being offered for the same server: 2GB (1x2GB) Single Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM 2GB (1x2GB) Dual Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM Given the option of Single Rank vs. Dual Rank or Dual Rank vs. Quad Rank is one always: Faster? Cheaper? Higher Bandwidth?

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  • Is this a good approach to address double-base64-encoding?

    - by Freiheit
    My software understands attachments, like PNGs attached to user records. These attachments are usually sent in from outside sources as a Base64 encoded string. The database stores whatever data it is given, Base64 encoded or not. When I serve up the attachment for download I do this: if (Base64.isBase64(data)) { data = Base64.decodeBase64(data); } There is a potential for data that is double encoded. For instance the sender of a message had base64 encoded data, then encoded it again when building the message to send to me. I think the following code would address that circumstance: while (Base64.isBase64(data)) { data = Base64.decodeBase64(data); } So if data is encoded multiple times, it would be decoded until its in its 'raw' state and then served up for download. Is this approach an acceptable way to address that problem? Ideally some sort of checking could happen at the edge when I receive attachment data, but that will take more time. This looping seems to be a faster way to do it. The 'Base64' library is Apache Commons: http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html I trust it to properly identify Base64 encoded data.

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  • How can I put double quotes inside a string within an ajax JSON response from php?

    - by karlthorwald
    I receive a JSON response in an Ajax request from the server. This way it works: { "a" = "1", "b" = "hello 'kitty'" } But I did not succeed in putting double quotes around kitty. When I convert " to \x22 in the Ajax response, it is still interpreted as " by JavaScript and I cannot parse the JSON. Should I also escape the \ and unescape later (which would be possible)? How to do this? Edit: I am not sure if i expressed it well: I want this string inside of "b" after the parse: hello "kitty" If necessary I could also add an additional step after the parse to convert "b", but I guess it is not necessary, there is a more elegant way so this happens automatically? Edit2: The ajax page is generated by php. I tried several things now to create the value of b, all result in JSON parse error on the page: $b = 'hello "kitty"'; // no 1: //$b = str_replace('"',"\x22",$b); // or no 2: // $b = addslashes($b); // or no 3: //$b = str_replace('"','\"',$b); // or no 4: $b = str_replace('"','\\"',$b); echo '"b" : "' . $b . '"';

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  • How to efficiently convert String, integer, double, datetime to binary and vica versa?

    - by Ben
    Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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  • "Forced constness" in std::map<std::vector<int>,double> > ?

    - by Peter Jansson
    Consider this program: #include <map> #include <vector> typedef std::vector<int> IntVector; typedef std::map<IntVector,double> Map; void foo(Map& m,const IntVector& v) { Map::iterator i = m.find(v); i->first.push_back(10); }; int main() { Map m; IntVector v(10,10); foo(m,v); return 0; } Using g++ 4.4.0, I get his compilation error: test.cpp: In function 'void foo(Map&, const IntVector&)': test.cpp:8: error: passing 'const std::vector<int, std::allocator<int> >' as 'this' argument of 'void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = int, _Alloc = std::allocator<int>]' discards qualifiers I would expect this error if I was using Map::const_iterator inside foo but not using a non-const iterator. What am I missing, why do I get this error?

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  • How can I prevent double file uploading with Amazon S3?

    - by Tony
    I decided to use Amazon S3 for document storage for an app I am creating. One issue I run into is while I need to upload the files to S3, I need to create a document object in my app so my users can perform CRUD actions. One solution is to allow for a double upload. A user uploads a document to the server my Rails app lives on. I validate and create the object, then pass it on to S3. One issue with this is progress indicators become more complicated. Using most out-of-the-box plugins would show the client that file has finished uploading because it is on my server, but then there would be a decent delay when the file was going from my server to S3. This also introduces unnecessary bandwidth (at least it does not seem necessary) The other solution I am thinking about is to upload the file directly to S3 with one AJAX request, and when that is successful, make a second AJAX request to store the object in my database. One issue here is that I would have to validate the file after it is uploaded which means I have to run some clean up code in S3 if the validation fails. Both seem equally messy. Does anyone have something more elegant working that they would not mind sharing? I would imagine this is a common situation with "cloud storage" being quite popular today. Maybe I am looking at this wrong.

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  • Formatting the output of a custom tool so I can double click an error in Visual Studio and the file opens

    - by Ben Scott
    I've written a command line tool that preprocesses a number of files then compiles them using CodeDom. The tool writes a copyright notice and some progress text to the standard output, then writes any errors from the compilation step using the following format: foreach (var err in results.Errors) { // err is CompilerError var filename = "Path\To\input_file.xprt"; Console.WriteLine(string.Format( "{0} ({1},{2}): {3}{4} ({5})", filename, err.Line, err.Column, err.IsWarning ? "" : "ERROR: ", err.ErrorText, err.ErrorNumber)); } It then writes the number of errors, like "14 errors". This is an example of how the error appears in the console: Path\To\input_file.xrpt (73,28): ERROR: An object reference is required for the non-static field, method, or property 'Some.Object.get' (CS0120) When I run this as a custom tool in VS2008 (by calling it in the post-build event command line of one of my project's assemblies), the errors appear nicely formatted in the Error List, with the correct text in each column. When I roll over the filename the fully qualified path pops up. The line and column are different to the source file because of the preprocessing which is fine. The only thing that stands out is that the Project given in the list is the one that has the post-build event. The problem is that when I double click an error, nothing happens. I would have expected the file to open in the editor. I'm vaugely aware of the Microsoft.VisualStudio.Shell.Interop namespace but I think it should be possible just by writing to the standard output.

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  • Why is my Android app force closing when I try to check if an EditText has a double

    - by user336861
    Scanner scanner = new Scanner(lapsPerMile_st); if (!scanner.hasNextDouble()) { Context context = getApplicationContext(); String msg = "Please Enter Digits and Decmials Only"; int duration = Toast.LENGTH_LONG; Toast.makeText(context, msg, duration).show(); lapsPerMileEditText.setText(""); return; } else { //Edit box has only digits, Set data and display stats data.setLapsPerMile(Integer.parseInt(lapsPerMile_st)); lapsRunLabel.setVisibility(0); lapsRunTextView.setText(Integer.toString(data.getLapsRun())); milesRunLabel.setVisibility(0); milesRunTextView.setText(Double.toString(data.getLapsRun()/data.getLapsPerMile())); } <EditText android:id="@+id/mileCount" android:layout_width="100dp" android:layout_height="wrap_content" android:layout_marginTop="110dp" android:inputType="numberDecimal" android:maxLength="4" /> For some reason if I enter a non decimal number such as 3, or 5, it works fine but when I enter a floating point such as 3.4 or 5.8 it force closes. I cant seem to figure out whats going on. Any ideas? Thanks

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  • How to efficiently get highest & lowest values from a List<double?>, and then modify them?

    - by DaveDev
    I have to get the sum of a list of doubles. If the sum is 100, I have to decrement from the highest number until it's = 100. If the sum is < 100, I have to increment the lowest number until it's = 100. I can do this by looping though the list, assigning the values to placeholder variables and testing which is higher or lower but I'm wondering if any gurus out there could suggest a super cool & efficient way to do this? The code below basically outlines what I'm trying to achieve: var splitValues = new List<double?>(); splitValues.Add(Math.Round(assetSplit.EquityTypeSplit() ?? 0)); splitValues.Add(Math.Round(assetSplit.PropertyTypeSplit() ?? 0)); splitValues.Add(Math.Round(assetSplit.FixedInterestTypeSplit() ?? 0)); splitValues.Add(Math.Round(assetSplit.CashTypeSplit() ?? 0)); var listSum = splitValues.Sum(split => split.Value); if (listSum != 100) { if (listSum > 100) { // how to get highest value and decrement by 1 until listSum == 100 // then reassign back into the splitValues list? var highest = // ?? } else { // how to get lowest where value is > 0, and increment by 1 until listSum == 100 // then reassign back into the splitValues list? var lowest = // ?? } } update: the list has to remain in the same order as the items are added.

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  • Convert RGB value to HSV

    - by marionmaiden
    I've found a method on the Internet to convert RGB values to HSV values. Unfortunately, when the values are R=G=B, I'm getting a NaN, because of the 0/0 operation. Do you know if there is an implemented method for this conversion in Java, or what do I have to do when I get the 0/0 division to get the right value of the HSV? Here comes my method, adapted from some code on the Internet: public static double[] RGBtoHSV(double r, double g, double b){ double h, s, v; double min, max, delta; min = Math.min(Math.min(r, g), b); max = Math.max(Math.max(r, g), b); // V v = max; delta = max - min; // S if( max != 0 ) s = delta / max; else { s = 0; h = -1; return new double[]{h,s,v}; } // H if( r == max ) h = ( g - b ) / delta; // between yellow & magenta else if( g == max ) h = 2 + ( b - r ) / delta; // between cyan & yellow else h = 4 + ( r - g ) / delta; // between magenta & cyan h *= 60; // degrees if( h < 0 ) h += 360; return new double[]{h,s,v}; }

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  • SQLiteDataAdapter Fill exception C# ADO.NET

    - by Lirik
    I'm trying to use the OleDb CSV parser to load some data from a CSV file and insert it into a SQLite database, but I get an exception with the OleDbAdapter.Fill method and it's frustrating: An unhandled exception of type 'System.Data.ConstraintException' occurred in System.Data.dll Additional information: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. Here is the source code: public void InsertData(String csvFileName, String tableName) { String dir = Path.GetDirectoryName(csvFileName); String name = Path.GetFileName(csvFileName); using (OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + dir + @";Extended Properties=""Text;HDR=No;FMT=Delimited""")) { conn.Open(); using (OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * FROM " + name, conn)) { QuoteDataSet ds = new QuoteDataSet(); adapter.Fill(ds, tableName); // <-- Exception here InsertData(ds, tableName); // <-- Inserts the data into the my SQLite db } } } class Program { static void Main(string[] args) { SQLiteDatabase target = new SQLiteDatabase(); string csvFileName = "D:\\Innovations\\Finch\\dev\\DataFeed\\YahooTagsInfo.csv"; string tableName = "Tags"; target.InsertData(csvFileName, tableName); Console.ReadKey(); } } The "YahooTagsInfo.csv" file looks like this: tagId,tagName,description,colName,dataType,realTime 1,s,Symbol,symbol,VARCHAR,FALSE 2,c8,After Hours Change,afterhours,DOUBLE,TRUE 3,g3,Annualized Gain,annualizedGain,DOUBLE,FALSE 4,a,Ask,ask,DOUBLE,FALSE 5,a5,Ask Size,askSize,DOUBLE,FALSE 6,a2,Average Daily Volume,avgDailyVolume,DOUBLE,FALSE 7,b,Bid,bid,DOUBLE,FALSE 8,b6,Bid Size,bidSize,DOUBLE,FALSE 9,b4,Book Value,bookValue,DOUBLE,FALSE I've tried the following: Removing the first line in the CSV file so it doesn't confuse it for real data. Changing the TRUE/FALSE realTime flag to 1/0. I've tried 1 and 2 together (i.e. removed the first line and changed the flag). None of these things helped... One constraint is that the tagId is supposed to be unique. Here is what the table look like in design view: Can anybody help me figure out what is the problem here?

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  • CIL and JVM Little endian to big endian in c# and java

    - by Haythem
    Hello, I am using on the client C# where I am converting double values to byte array. I am using java on the server and I am using writeDouble and readDouble to convert double values to byte arrays. The problem is the double values from java at the end are not the double values at the begin giving to c# writeDouble in Java Converts the double argument to a long using the doubleToLongBits method , and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first. DoubleToLongBits Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout. The Program on the server is waiting of 64-102-112-0-0-0-0-0 from C# to convert it to 1700.0 but he si becoming 0000014415464 from c# after c# converted 1700.0 this is my code in c#: class User { double workingStatus; public void persist() { byte[] dataByte; using (MemoryStream ms = new MemoryStream()) { using (BinaryWriter bw = new BinaryWriter(ms)) { bw.Write(workingStatus); bw.Flush(); bw.Close(); } dataByte = ms.ToArray(); for (int j = 0; j < dataByte.Length; j++) { Console.Write(dataByte[j]); } } public double WorkingStatus { get { return workingStatus; } set { workingStatus = value; } } } class Test { static void Main() { User user = new User(); user.WorkingStatus = 1700.0; user.persist(); } thank you for the help.

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  • C function const multidimensional-array argument strange warning

    - by rogi
    Ehllo, I'm getting some strange warning about this code: typedef double mat4[4][4]; void mprod4(mat4 r, const mat4 a, const mat4 b) { /* yes, function is empty */ } int main() { mat4 mr, ma, mb; mprod4(mr, ma, mb); } gcc output as follows: $ gcc -o test test.c test.c: In function 'main': test.c:13: warning: passing argument 2 of 'mprod4' from incompatible pointer type test.c:4: note: expected 'const double (*)[4]' but argument is of type 'double (*)[4]' test.c:13: warning: passing argument 3 of 'mprod4' from incompatible pointer type test.c:4: note: expected 'const double ()[4]' but argument is of type 'double ()[4]' defining the function as: void mprod4(mat4 r, mat4 a, mat4 b) { } OR defining matrices at main as: mat4 mr; const mat4 ma; const mat4 mb; OR calling teh function in main as: mprod4(mr, (const double(*)[4])ma, (const double(*)[4])mb); OR even defining mat4 as: typedef double mat4[16]; make teh warning go away. Wat is happening here? Am I doing something invalid? gcc version is 4.4.3 if relevant. Thanks for your attention.

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  • Call by Reference Function in C

    - by Chad
    Hello everyone, I would just like a push in the right direction here with my homework assignment. Here is the question: (1) Write a C function called input which returns void, this function prompts the user for input of two integers followed by a double precision value. This function reads these values from the keyboard and finds the product of the two integers entered. The function uses call by reference to communicate the values of the three values read and the product calculated back to the main program. The main program then prints the three values read and the product calculated. Provide test results for the input: 3 5 23.5. Do not use arrays or global variables in your program. And here is my code: #include <stdio.h> #include <stdlib.h> void input(int *day, int *month, double *k, double *pro); int main(void){ int i,j; double k, pro; input(&i, &j, &k, &pro); printf("%f\n", pro); return 0; } void input(int *i, int *j, double *k, double *pro){ int x,y; double z; double product; scanf("%d", &x); scanf("%d", &y); scanf("%f", &z); *pro += (x * y * z); } I can't figure out how to reference the variables with pointers really, it is just not working out for me. Any help would be great!

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  • Java Arrays.equals() returns false for two dimensional arrays.

    - by Achilles
    Hi there, I was just curious to know - why does Arrays.equals(double[][], double[][]) return false? when in fact the arrays have the same number of elements and each element is the same? For example I performed the following test. ` [java] double[][] a, b; int size =5; a=new double[size][size]; b=new double[size][size]; for( int i = 0; i < size; i++ ) for( int j = 0; j < size; j++ ){ a[i][j]=1.0; b[i][j]=1.0; } if(Arrays.equals(a, b)) System.out.println("Equal"); else System.out.println("Not-equal"); [/java] ` Returns false and prints "Not-equal. on the other hand, if I have something like this: [java] double[] a, b; int size =5; a=new double[size]; b=new double[size]; for( int i = 0; i < size; i++ ){ a[i]=1.0; b[i]=1.0; } if(Arrays.equals(a, b)) System.out.println("Equal"); else System.out.println("Not-equal"); } [/java] returns true and prints "Equal". Does the method only work with single dimensions? if so, is there something similar for multi-dimensional arrays in Java?

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  • C++ Returning a Reference

    - by Devil Jin
    Consider the following code where I am returning double& and a string&. The thing works fine in the case of a double but not in the case of a string. Why is this difference in the behavior? In both the cases compiler does not even throws the Warning: returning address of local variable or temporary as I am returning a reference. #include <iostream> #include <string> using namespace std; double &getDouble(){ double h = 46.5; double &hours = h; return hours; } string &getString(){ string str = "Devil Jin"; string &refStr = str; return refStr; } int main(){ double d = getDouble(); cout << "Double = " << d << endl; string str = getString(); cout << "String = " << str.c_str() << endl; return 0; } Output: $ ./a.exe Double = 46.5 String =

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  • Image resizing - sometimes very poor quality?!

    - by eWolf
    I'm resizing some images to the screen resolution of the user; if the aspect ratio is wrong, the image should be cut. My code looks like this: protected void ConvertToBitmap(string filename) { var origImg = System.Drawing.Image.FromFile(filename); var widthDivisor = (double)origImg.Width / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width; var heightDivisor = (double)origImg.Height / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height; int newWidth, newHeight; if (widthDivisor < heightDivisor) { newWidth = (int)((double)origImg.Width / widthDivisor); newHeight = (int)((double)origImg.Height / widthDivisor); } else { newWidth = (int)((double)origImg.Width / heightDivisor); newHeight = (int)((double)origImg.Height / heightDivisor); } var newImg = origImg.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero); newImg.Save(this.GetBitmapPath(filename), System.Drawing.Imaging.ImageFormat.Bmp); } In most cases, this works fine. But for some images, the result has an extremely poor quality. It looks like the would have been resized to something very small (thumbnail size) and enlarged again.. But the resolution of the image is correct. What can I do? Example orig image: Example resized image: Note: I have a WPF application but I use the WinForms function for resizing because it's easier and because I already need a reference to System.Windows.Forms for a tray icon.

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  • C ] How can I handle weird errors from calculating acos / sin / atan2?

    - by Phrixus
    Has anyone seen this weird value while handling sin / cos/ tan / acos.. math stuff? ===THE WEIRD VALUE=== -1.#IND00 ===================== void inverse_pos(double x, double y, double& theta_one, double& theta_two) { // Assume that L1 = 350 and L2 = 250 double B = sqrt(x*x + y*y); double angle_beta = atan2(y, x); double angle_alpha = acos((L2*L2 - B*B - L1*L1) / (-2*B*L1)); theta_one = angle_beta + angle_alpha; theta_two = atan2((y-L1*sin(theta_one)), (x-L1*cos(theta_one))); } This is the code I was working on. In a particular condition - like when x & y are 10 & 10, this code stores -1.#IND00 into theta_one & theta_two. It doesn't look like either characters or numbers :( Without a doubt, atan2 / acos / stuff are the problems. But the problem is, try and catch doesn't work either cuz those double variables have successfully stored some values in them. Moreover, the following calculations never complain about it and never break the program! I'm thinking of forcing to use this value somehow and make the entire program crash... So that I can catch this error.. Except for that idea, I have no idea how I should check whether these theta_one and theta_two variables have stored this crazy values. Any good ideas? Thank you in advance..

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  • give feedback on this pointer program

    - by JohnWong
    This is relatively simple program. But I want to get some feedback about how I can improve this program (if any), for example, unnecessary statements? #include<iostream> #include<fstream> using namespace std; double Average(double*,int); int main() { ifstream inFile("data2.txt"); const int SIZE = 4; double *array = new double(SIZE); double *temp; temp = array; for (int i = 0; i < SIZE; i++) { inFile >> *array++; } cout << "Average is: " << Average(temp, SIZE) << endl; } double Average(double *pointer, int x) { double sum = 0; for (int i = 0; i < x; i++) { sum += *pointer++; } return (sum/x); } The codes are valid and the program is working fine. But I just want to hear what you guys think, since most of you have more experience than I do (well I am only a freshman ... lol) Thanks.

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  • optimize output value using a class and public member

    - by wiso
    Suppose you have a function, and you call it a lot of times, every time the function return a big object. I've optimized the problem using a functor that return void, and store the returning value in a public member: #include <vector> const int N = 100; std::vector<double> fun(const std::vector<double> & v, const int n) { std::vector<double> output = v; output[n] *= output[n]; return output; } class F { public: F() : output(N) {}; std::vector<double> output; void operator()(const std::vector<double> & v, const int n) { output = v; output[n] *= n; } }; int main() { std::vector<double> start(N,10.); std::vector<double> end(N); double a; // first solution for (unsigned long int i = 0; i != 10000000; ++i) a = fun(start, 2)[3]; // second solution F f; for (unsigned long int i = 0; i != 10000000; ++i) { f(start, 2); a = f.output[3]; } } Yes, I can use inline or optimize in an other way this problem, but here I want to stress on this problem: with the functor I declare and construct the output variable output only one time, using the function I do that every time it is called. The second solution is two time faster than the first with g++ -O1 or g++ -O2. What do you think about it, is it an ugly optimization?

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  • How to mimic polymorphism in classes with template methods (c++)?

    - by davide
    in the problem i am facing i need something which works more or less like a polymorphic class, but which would allow for virtual template methods. the point is, i would like to create an array of subproblems, each one being solved by a different technique implemented in a different class, but holding the same interface, then pass a set of parameters (which are functions/functors - this is where templates jump up) to all the subproblems and get back a solution. if the parameters would be, e.g., ints, this would be something like: struct subproblem { ... virtual void solve (double& solution, double parameter)=0; } struct subproblem0: public subproblem { ... virtual void solve (double& solution, double parameter){...}; } struct subproblem1: public subproblem { ... virtual void solve (double* solution, double parameter){...}; } int main{ subproblem problem[2]; subproblem[0] = new subproblem0(); subproblem[1] = new subproblem1(); double argument0(0), argument1(1), sol0[2], sol1[2]; for(unsigned int i(0);i<2;++i) { problem[i]->solve( &(sol0[i]) , argument0); problem[i]->solve( &(sol1[i]) , argument1); } return 0; } but the problem is, i need the arguments to be something like Arg<T1,T2> argument0(f1,f2) and thus the solve method to be something of the likes of template<T1,T2> solve (double* solution, Arg<T1,T2> parameter) which cant obviously be declared virtual ( so cant be called from a pointer to the base class)... now i'm pretty stuck and don't know how to procede...

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