Exif Usercomment How To Alter An
When writing the tag it merely changes pre-allocated bytes. It does not modify, extend, or otherwise adulterate an images Exif metadata structure. Minimum length of I need to understand the basic concept of how to alter an exif tag and save the changed JPG file (using VB 2010 under Windows 7).The utility is conservative in its approach to writing the UserComment tag. We’re going to get started with how to read geotagged photographs using Python to make use of the data.MDMEXIFEXIF UserComment Property : Gets or sets a tag for Exif users to write keywords or comments on the image besides those in ImageDescription, and without the character code limitations of the ImageDescription tag. With the proliferation of digital cameras and smart phones with GPS receivers these images often include geolocation coordinates. The Exchangeable image file format (Exif) is a standard that’s been around since 1998 to include metadata in image file formats like JPEG, WAV, HEIC, and WEBP.
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Option Strict OnUsing fs As New IO.FileStream(_path, IO.FileMode.Open)Using img As Image = Image.FromStream(fs)Dim origFormat As ImageFormat = img.RawFormatFs.Write(ms.ToArray(), 0, CInt(ms. Imports System.Drawing.ImagingPrivate Const ExifUserComment As Integer = &H9286Private filename As String = "C:\TestFolder\MyImage.jpg"Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.ClickDim pi As PropertyItem = bmp.GetPropertyItem(ExifUserComment)TextBox1.Text = System.Text.Encoding.ASCII.GetString(pi.Value)MessageBox.Show("The file does not contain ExifUserComment.")Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.ClickDim b As Bitmap = Nothing Dim pi As PropertyItem = Nothing Using bmp As New Bitmap(filename) b = New Bitmap(bmp) For Each p As PropertyItem In bmp.PropertyItems Try b.SetPropertyItem(p) Catch ex As Exception End Try Next Try pi = bmp.GetPropertyItem(ExifUserComment) Dim bts() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox2.Text) pi.Len = bts.Length + 1 pi.Value = bts b.SetPropertyItem(pi) Catch ex As Exception MessageBox.Show("The file does not contain ExifUserComment.") pi = Nothing End Try End Using If pi IsNot Nothing Then b.Save(filename, Imaging.ImageFormat.Jpeg) End If b.Dispose() End SubHere i get the original user comment, then set a new user comment, and finally get the new comment i just added.If you say it can`t be done then i`ll try itThis should also work for images that dont already have the tag specified.Note you must also loop over the existing propertyItems and re-save them, when using the clone of the orig image Option Strict OnDim _path As String = "put a valid path to a jpeg image here"Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.LoadDim enc As System.Text.Encoding = System.Text.Encoding.UTF8Using img As Image = Image.FromFile(_path)I = img.GetPropertyItem(270) 'subject (title in german) in windows explorerI = CType(FormatterServices.GetUninitializedObject(GetType(PropertyItem)), PropertyItem)I.Type = 2 ' 1 also works, but is not shown in windows explorer, so I set it to 2 as an experiment (I dont know the types and I'm too tired now to look it up :-) )I.Value = enc.GetBytes("this is the new title" & ControlChars.NullChar)For Each j As PropertyItem In img.PropertyItems'If (j.Id &H100) And (j.Id &H101) And (j.Id &H11A) _' And (j.Id &H11B) And (j.Id &H102) ThenTry 'saving commented out, uncomment if your sure that the file may be overwritten'img2.Save(_path, System.Drawing.Imaging.ImageFormat.Jpeg)'Dim i2 As Imaging.PropertyItem = img2.GetPropertyItem(270)'MsgBox(i2.Value.Length.ToString & vbCrLf & enc.GetString(i2.Value))Here's a first version using the original image only, which doesnz need to copy all exisiting PropetyItems in a loop to the new picture.Remember to use with copiies of images when testing since it saves to the original fileNameEdit: Added the jpeg highQuality param-saving Option Strict OnDim newText As String = "this is the title"Using ms As MemoryStream = New MemoryStream()NewText = enc.GetString(i.Value).Substring(0, i.Len - 1) + " new"I.Value = enc.GetBytes(newText & ControlChars.NullChar)'save as png for best quality, the exif tags are correctly saved to png-format on my machine (win7)'if not, do as save as jpeg as below with the quality-parameterImg.Save(ms, System.Drawing.Imaging.ImageFormat.Png)Dim IIenc() As ImageCodecInfo = ImageCodecInfo.GetImageEncoders()EncParam.Param(0) = New EncoderParameter(Encoder.Quality, quality)If origFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg) ThenDim i2 As Imaging.PropertyItem = img2.GetPropertyItem(270)MsgBox(i2.Value.Length.ToString & vbCrLf & enc.GetString(i2.Value))Here's the second version of the third version :-)Remember to use with copies of images when testing since it saves to the original fileNameEdit: set the length of the stream. You could set up a dummy image with all the properties you want so you can copy them to the image you want to add it to if theImage does not have the PropertyItem.
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