Develop Reference

How can i convert a file .png to a Bitmap? Nothing works for me. Error "'Failed to decode image. The provided image must be a Bitmap.'" Xamarin.forms

I'm working with Xamarin in the part of Xamarin.Forms i need to convert a file ("image.png") to a Bitmap because when project run its enter in "break mode" and show me this message "Java.Lang.IllegalArgumentException: 'Failed to decode image. The provided image must be a Bitmap.'". So i tried to convert the file in many ways like:
1_ Using methods from System.Drawing.Bitmap but it's show this exception "This operation is not supported in this platform"
2_ Cannot use Android.Graphics because i'm working in xamarin.forms not in xamarin.android.
3_ I tried to convert the "image.png" into a base64 or byte[] array and then into a bitmap but the problem is the same like in first problem because to convert from byte[] array or base64 to a Bitmap i have use methods from System.Drawing.Bitmap.
4_ I tried using the library SkiaSharp but i don't have success because i don't found so much information about how to convert .png to SKBitmap and then convert SKBitmap to Bitmap (even i don't know if this is possible).
5_ Finally i converted "image.png" to a "image.bmp" with an app and use the file .bmp in my project but it doesn't work too.
the "image.png" i have to save in a string variable, well that's the idea.
If you have a solution with SkiaSharp o whatever i will glad
EDIT
here is a part of my code, i just save in a variable the image
Icon = "pin_blue.png";
//i can't use a path because in xamarin you have many size from the same
//image for the different size of the screen
EDIT 2 This is my method to show the pins in google maps
private void ShowPins(List<PointsOfInterest> resultPointsOfInterest)
{
if (resultPointsOfInterest != null && resultPointsOfInterest.Any())
{
var location = Geolocation.GetLastKnownLocationAsync();
PointsOfInterest position = new PointsOfInterest();
if (location != null)
{
position.ccsm0166latitud = location.Result.Latitude;
position.ccsm0166longitud = location.Result.Longitude;
}
else {
position = resultPointsOfInterest.First();
}
//Distance = Distance.FromKilometers(new Random().Next(23,35));
Distance = Distance.FromKilometers(3);
Position = new Position(position.ccsm0166latitud, position.ccsm0166longitud);
PinsFiltered= Pins = new List<PinCustom>(resultPointsOfInterest.Select(
x => new PinCustom()
{
Position =
new Position(x.ccsm0166latitud, x.ccsm0166longitud),
Address = x.ccsm0166direccion,
Label = x.ccsm0166nombre,
Type = PinType.Place,
TypePointOfInterest = x.ccsm0166tipositio,
IconBM = Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branch ? PinCustom.ConvertToBitmap("pin_blue.png") :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branch ? "pin_blue.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours2 ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.branchWithExtendedHours3 ? "pin_black.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.selfServiceTerminal ? "pin_green.png" :
Int32.Parse(x.ccsm0166tipositio) == (int)PointOfInterestType.atmServBox ? "pin_yellow.png" : string.Empty
}).ToList());
}
else
{
Pins = new List<PinCustom>();
}
}
This is the class Pin where i save the image
public class PinCustom : Pin
{
public string TypePointOfInterest { get; set; }
public string Icon { get; set; }
public Bitmap { get; set; }
//Here i create this variable to save a bitmap but i don't know if i do the things well
}
this is the icon .png i want to show in googlemaps
Pin Blue Image

To open your file and convert it to byte array:
string directory = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, Android.OS.Environment.DirectoryDownloads);
// or your image directory, just replace it
var stream = File.OpenWrite(Path.Combine(directory, "image.png"));
byte[] buff = ConvertStreamToByteArray(stream);
stream.Close();
public static byte[] ConvertStreamToByteArray(Stream stream)
{
byte[] byteArray = new byte[16 * 1024];
using (MemoryStream mStream = new MemoryStream())
{
int bit;
while ((bit = stream.Read(byteArray, 0, byteArray.Length)) > 0)
{
mStream.Write(byteArray, 0, bit);
}
return mStream.ToArray();
}
}
then, to pass this byte array to SKBitmap:
SKBitmap bmp = SKBitmap.Decode(buff);
EDIT:
If you want to try without ConvertStreamToByteArray():
byte[] buff = null;
stream.Write(buff, 0, buff.Length);
This Write will depend of the type of your stream. In this example, I'm using FileStream.
EDIT 2:
string resourceID = "image.png";
Assembly assembly = GetType().GetTypeInfo().Assembly;
using (Stream stream = assembly.GetManifestResourceStream(resourceID))
{
resourceBitmap = SKBitmap.Decode(stream);
SKBitmap bmp = SKImage.FromBitmap(resourceBitmap);
}
and then you can use this bitmap to draw and fill your SKCanvas:
canvas.DrawBitmap(bmp, 0, 0);

Use ffmpeg
command for this: ffmpeg -i image.png image.bmp

i have 5 types of pins (pins are the image .png) when i put the pins
in format .png
if you want to custom the pins in your map, you can simply use Custom Renderers to achieve this.
The icon used to represent a marker can be customized by calling the MarkerOptions.SetIcon method. This can be accomplished by overriding the CreateMarker method, which is invoked for each Pin that's added to the map:
protected override MarkerOptions CreateMarker(Pin pin)
{
var marker = new MarkerOptions();
marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
marker.SetTitle(pin.Label);
marker.SetSnippet(pin.Address);
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.pin));
return marker;
}
If you want to display different icons, you can refer to the following code:
protected override MarkerOptions CreateMarker(Pin pin)
{
var marker = new MarkerOptions();
marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
marker.SetTitle(pin.Label);
marker.SetSnippet(pin.Address);
var customPin = (Element as CustomMap).CustomPins.FirstOrDefault(p => p.Position == pin.Position);
if (customPin != null)
{
if (customPin.IconType == "corporate")
{
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.corporate));
}
else if (customPin.IconType == "pickup")
{
marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.bus));
}
}
return marker;
}
For more, check:Customizing the Marker.

Digit recognition with Tesseract OCR and c#

I use Tesseract and C# to read digits. Everything works well except for the number "8". Tesseract can not read the "8" Digit.
This is the picture I send to tesseract :
And tesseract reads "50005550055".
this is my method :
public string Process(Bitmap bitmap, MetaTraderObjects metaObjects, bool isNumber = false)
{
try
{
var graphicLib = new GraphicLib();
bitmap = graphicLib.PerformReadingTextEffects(bitmap.ToBytes(), metaObjects).ToBitmap();
var result = "";
var enginePath = Const.BaseAppPath + "\\tessdata";
using (var engine = new TesseractEngine(enginePath, "eng", EngineMode.Default))
{
var ver = engine.Version;
using (var img = Pix.LoadTiffFromMemory(graphicLib.ConvertBitMapToByteArray(bitmap.ToBytes())))
{
using (var page = engine.Process(img,(PageSegMode)8))
{
var text = page.GetText();
result = TextReformer.Reform(text, isNumber);
MemoryStream ms = new MemoryStream(bitmap.ToBytes());
Image i = Image.FromStream(ms);
}
}
}
return result;
}
catch (Exception ex)
{
ExceptionLog.Handel(ex);
return null;
}
}
How can I tell Tesseract that the vertical rod is a "8"?

I recommend you use the latest version of Tesseract. It could perform better.
Tesseract 4.1.0

Render a barcode in ASP.NET Web Form

i am trying to show the barcode in asp.net page. already download the zen barcode render with sample code. i tried the sample it is working fine with me. once i try in my code barcode label is showing empty. i checked with sample code and mine i did not find any difference , only data transfer is the different. this is what i tried.
<barcode:BarcodeLabel ID="BarcodeLabel1" runat="server" BarcodeEncoding="Code39NC" LabelVerticalAlign="Bottom" Text="12345"></barcode:BarcodeLabel>
if (!IsPostBack)
{
List<string> symbologyDataSource = new List<string>(
Enum.GetNames(typeof(BarcodeSymbology)));
symbologyDataSource.Remove("Unknown");
barcodeSymbology.DataSource = symbologyDataSource;
barcodeSymbology.DataBind();
}
this is the function
BarcodeSymbology symbology = BarcodeSymbology.Unknown;
if (barcodeSymbology.SelectedIndex != 0)
{
symbology = (BarcodeSymbology)1;
}
symbology = (BarcodeSymbology)1;
string text = hidID.Value.ToString();
string scaleText = "1";
int scale;
if (!int.TryParse(scaleText, out scale))
{
if (symbology == BarcodeSymbology.CodeQr)
{
scale = 3;
}
else
{
scale = 1;
}
}
else if (scale < 1)
{
scale = 1;
}
if (!string.IsNullOrEmpty(text) && symbology != BarcodeSymbology.Unknown)
{
barcodeRender.BarcodeEncoding = symbology;
barcodeRender.Scale = 1;
barcodeRender.Text = text;
}
symbology is set as Code39NC from the dropdown. scale is 1 and text is coming from other form the value is passing as well. still the bacodelable is showing only value not the barcode picture.

Here are two code samples using ZXing to create a (QR) barcode as both an image and as a base64 encoded string. Both of these options can be used with an <img /> tag to embed the barcode in the page.
This is not an ASP.NET control. It is a library that creates barcodes from text.
// First Text to QR Code as an image
public byte[] ToQRAsGif(string content)
{
var barcodeWriter = new BarcodeWriter
{
Format = BarcodeFormat.QR_CODE,
Options = new EncodingOptions
{
Height = this._h,
Width = this._w,
Margin = 2
}
};
using (var bitmap = barcodeWriter.Write(content))
using (var stream = new MemoryStream())
{
bitmap.Save(stream, ImageFormat.Gif);
stream.Position = 0;
return stream.GetBuffer();
}
}
// From Text to QR Code as base64 string
public string ToQRAsBase64String(string content)
{
var barcodeWriter = new BarcodeWriter
{
Format = BarcodeFormat.QR_CODE,
Options = new EncodingOptions
{
Height = _h,
Width = _w,
Margin = 2
}
};
using (var bitmap = barcodeWriter.Write(content))
using (var stream = new MemoryStream())
{
bitmap.Save(stream, ImageFormat.Gif);
return String.Format("data:image/gif;base64,{0}", Convert.ToBase64String(stream.ToArray()));
}
}
Hope this helps! Happy coding.
UPDATE: Here is the link to their product page on codeplex: https://zxingnet.codeplex.com/

Write metadata to both jpg and png

I need to add a metadata tag (description) to uploaded images.
I have found out this answer: https://stackoverflow.com/a/1764913/6776 which works great for JPG files, but not for PNG.
private string Tag = "test meta data";
private static Stream TagImage(Stream input, string type)
{
bool isJpg = type.EndsWith("jpg", StringComparison.InvariantCultureIgnoreCase) || type.EndsWith("jpeg", StringComparison.InvariantCultureIgnoreCase);
bool isPng = type.EndsWith("png", StringComparison.InvariantCultureIgnoreCase);
BitmapDecoder decoder = null;
if (isJpg)
{
decoder = new JpegBitmapDecoder(input, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
}
else if (isPng)
{
decoder = new PngBitmapDecoder(input, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
}
else
{
return input;
}
// modify the metadata
BitmapFrame bitmapFrame = decoder.Frames[0];
BitmapMetadata metaData = (BitmapMetadata)bitmapFrame.Metadata.Clone();
metaData.Subject = Tag;
metaData.Comment = Tag;
metaData.Title = Tag;
// get an encoder to create a new jpg file with the new metadata.
BitmapEncoder encoder = null;
if (isJpg)
{
encoder = new JpegBitmapEncoder();
}
else if (isPng)
{
encoder = new PngBitmapEncoder();
}
encoder.Frames.Add(BitmapFrame.Create(bitmapFrame, bitmapFrame.Thumbnail, metaData, bitmapFrame.ColorContexts));
// Save the new image
Stream output = new MemoryStream();
encoder.Save(output);
output.Seek(0, SeekOrigin.Begin);
return output;
}
It works great when I upload a jpg, but with a png, at the metaData.Subject = Tag line, it throws a System.NotSupportedException (this codec does not support the specified property).
Update
It seems I have to use a different method based on the image format:
if (isJpg)
{
metaData.SetQuery("/app1/ifd/exif:{uint=270}", Tag);
}
else
{
metaData.SetQuery("/tEXt/{str=Description}", Tag);
}
Based on the available formats' queries the first should work for both formats. The second doesn't really work either (it creates the metadata in the image but does not save its value).
If I try to use the first method (/app1/ifd/exif) for PNG, at the encoder.Save line I get a not supported exception, "no imaging component suitable".

I solved it using pngcs library (you need to rename the downloaded dll to "pngcs.dll")
Here is how I implemented it:
using Hjg.Pngcs; // https://code.google.com/p/pngcs/
using Hjg.Pngcs.Chunks;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace MarkerGenerator.Utils
{
class PngUtils
{
public string getMetadata(string file, string key)
{
PngReader pngr = FileHelper.CreatePngReader(file);
//pngr.MaxTotalBytesRead = 1024 * 1024 * 1024L * 3; // 3Gb!
//pngr.ReadSkippingAllRows();
string data = pngr.GetMetadata().GetTxtForKey(key);
pngr.End();
return data; ;
}
public static void addMetadata(String origFilename, Dictionary<string, string> data)
{
String destFilename = "tmp.png";
PngReader pngr = FileHelper.CreatePngReader(origFilename); // or you can use the constructor
PngWriter pngw = FileHelper.CreatePngWriter(destFilename, pngr.ImgInfo, true); // idem
//Console.WriteLine(pngr.ToString()); // just information
int chunkBehav = ChunkCopyBehaviour.COPY_ALL_SAFE; // tell to copy all 'safe' chunks
pngw.CopyChunksFirst(pngr, chunkBehav); // copy some metadata from reader
foreach (string key in data.Keys)
{
PngChunk chunk = pngw.GetMetadata().SetText(key, data[key]);
chunk.Priority = true;
}
int channels = pngr.ImgInfo.Channels;
if (channels < 3)
throw new Exception("This example works only with RGB/RGBA images");
for (int row = 0; row < pngr.ImgInfo.Rows; row++)
{
ImageLine l1 = pngr.ReadRowInt(row); // format: RGBRGB... or RGBARGBA...
pngw.WriteRow(l1, row);
}
pngw.CopyChunksLast(pngr, chunkBehav); // metadata after the image pixels? can happen
pngw.End(); // dont forget this
pngr.End();
File.Delete(origFilename);
File.Move(destFilename, origFilename);
}
public static void addMetadata(String origFilename,string key,string value)
{
Dictionary<string, string> data = new Dictionary<string, string>();
data.Add(key, value);
addMetadata(origFilename, data);
}
}
}

The library CompactExifLib can write EXIF tags in JPEG, TIFF and PNG files:
https://www.codeproject.com/Articles/5251929/CompactExifLib-Access-to-EXIF-Tags-in-JPEG-TIFF-an
It is written purely in C# and can be used for free.
Note: I am the author of this library.

The PNG-format does not support metadata :(
But XMP does, which might be of help when converting between JPEGs, with EXIF-metadata, and PNG.

Windows Forms: How to directly bind a Bitmap to a PictureBox?

I'm just trying to build a small C# .Net 4.0 application using Windows Forms (WPF I don't know at all, Windows Forms at least a little :-) ).
Is it possible to directly bind a System.Drawing.Bitmap object to the Image property of a PictureBox? I tried to use PictureBox.DataBindings.Add(...) but this doesn't seem to work.
How can I do this?
Thanks and best regards,
Oliver

This works for me:
Bitmap bitmapFromFile = new Bitmap("C:\\temp\\test.bmp");
pictureBox1.Image = bitmapFromFile;
or, in one line:
pictureBox1.Image = new Bitmap("C:\\temp\\test.bmp");
You might be overcomplicating this - according to the MSDN documentation, you can simple assign the bitmap directly to the PictureBox.Image property.

You can use the PictureBox.DataBindings.Add(...)
The trick is to create a separate property on the object you are binding to to handle the conversion between null and and empty picture.
I did it this way.
In my form load I used
this.PictureBox.DataBindings.Add(new Binding("Visible", this.bindingSource1, "HasPhoto", false, DataSourceUpdateMode.OnPropertyChanged));
this.PictureBox.DataBindings.Add(new Binding("Image", this.bindingSource1, "MyPhoto",false, DataSourceUpdateMode.OnPropertyChanged));
In my object I have the following
[NotMapped]
public System.Drawing.Image MyPhoto
{
get
{
if (Photo == null)
{
return BlankImage;
}
else
{
if (Photo.Length == 0)
{
return BlankImage;
}
else
{
return byteArrayToImage(Photo);
}
}
}
set
{
if (value == null)
{
Photo = null;
}
else
{
if (value.Height == BlankImage.Height) // cheating
{
Photo = null;
}
else
{
Photo = imageToByteArray(value);
}
}
}
}
[NotMapped]
public Image BlankImage {
get
{
return new Bitmap(1,1);
}
}
public static byte[] imageToByteArray(Image imageIn)
{
MemoryStream ms = new MemoryStream();
imageIn.Save(ms, ImageFormat.Gif);
return ms.ToArray();
}
public static Image byteArrayToImage(byte[] byteArrayIn)
{
MemoryStream ms = new MemoryStream(byteArrayIn);
Image returnImage = Image.FromStream(ms);
return returnImage;
}

You can do:
System.Drawing.Bitmap bmp = new System.Drawing.Bitmap("yourfile.bmp");
picturebox1.Image = bmp;