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dotnet drawing api : How to use GetThumbnailImage without embedded thumbnail?
Just create your thumbnail manually by creating an image the size of the
desired thumbnail, obtaining a Graphics object from it using Graphics.FromImage and drawing the original image to the thumbnail at the appropriate size. -- Bob Powell [MVP] Visual C#, System.Drawing Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "George Nevsky" <apokriffree@hotbox.ru> wrote in message news:ONYhvK35EHA.3124@TK2MSFTNGP11.phx.gbl... > I wish to use GetThumbnailImage method of Image object to downsize an image > but I don't want to use embedded thumbnail which can be in original image > file. > > > > I know probably it isn't best in the world way but I like it. It works > absolutely fine for my purposes. It is very simple. It works fine with > indexed color images like GIF as well as with true color images like JPEG. > It is pretty fast. But it has one horrible thing. It is using embedded > thumbnail (if there is one) which can be ugly. > > How to tell to GDI+ don't use embedded thumbnail? > >
I wish to use GetThumbnailImage method of Image object to downsize an image
but I don't want to use embedded thumbnail which can be in original image file. I know probably it isn't best in the world way but I like it. It works absolutely fine for my purposes. It is very simple. It works fine with indexed color images like GIF as well as with true color images like JPEG. It is pretty fast. But it has one horrible thing. It is using embedded thumbnail (if there is one) which can be ugly. How to tell to GDI+ don't use embedded thumbnail?
I use the following code to create thumbnails and to enlarge images.
Public Shared Function ResizeBitmap( _ ByVal bmpBitmap As Bitmap, _ ByVal snglBoundingWidth As Single, _ ByVal snglBoundingHeight As Single, _ Optional ByVal blnHighQuality As Boolean = False) As Bitmap Dim snglNewWidth, snglNewHeight As Single If snglBoundingWidth > 1 And snglBoundingHeight > 1 Then If (bmpBitmap.Height / bmpBitmap.Width) > (snglBoundingHeight / snglBoundingWidth) Then snglNewHeight = Int(snglBoundingHeight) snglNewWidth = Int((bmpBitmap.Width / bmpBitmap.Height) * snglNewHeight) Else snglNewWidth = Int(snglBoundingWidth) snglNewHeight = Int((bmpBitmap.Height / bmpBitmap.Width) * snglNewWidth) End If Else snglNewWidth = bmpBitmap.Width * snglBoundingWidth snglNewHeight = bmpBitmap.Height * snglBoundingHeight End If Dim bmpNewBitmap As System.Drawing.Bitmap bmpNewBitmap = New Bitmap(bmpBitmap, snglNewWidth, snglNewHeight) If blnHighQuality = True Then Dim g As Graphics = Graphics.FromImage(bmpNewBitmap) g.InterpolationMode = Drawing.Drawing2D.InterpolationMode.HighQualityBicubic g.DrawImage(bmpBitmap, 0, 0, bmpNewBitmap.Width, bmpNewBitmap.Height) End If Return bmpNewBitmap End Function
But Graphics.FromImage doesn't work with indexed color pictures ...
[quoted text, click to view] "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message news:OCu3TN35EHA.1564@TK2MSFTNGP09.phx.gbl... > Just create your thumbnail manually by creating an image the size of the > desired thumbnail, obtaining a Graphics object from it using > Graphics.FromImage and drawing the original image to the thumbnail at the > appropriate size. > > -- > Bob Powell [MVP] > Visual C#, System.Drawing > > Find great Windows Forms articles in Windows Forms Tips and Tricks > http://www.bobpowell.net/tipstricks.htm > > Answer those GDI+ questions with the GDI+ FAQ > http://www.bobpowell.net/faqmain.htm > > All new articles provide code in C# and VB.NET. > Subscribe to the RSS feeds provided and never miss a new article. > > > > > > "George Nevsky" <apokriffree@hotbox.ru> wrote in message > news:ONYhvK35EHA.3124@TK2MSFTNGP11.phx.gbl... >> I wish to use GetThumbnailImage method of Image object to downsize an > image >> but I don't want to use embedded thumbnail which can be in original image >> file. >> >> >> >> I know probably it isn't best in the world way but I like it. It works >> absolutely fine for my purposes. It is very simple. It works fine with >> indexed color images like GIF as well as with true color images like >> JPEG. >> It is pretty fast. But it has one horrible thing. It is using embedded >> thumbnail (if there is one) which can be ugly. >> >> How to tell to GDI+ don't use embedded thumbnail? >> >> > >
It's not the indexed image that you should use.
Image i=Image.FromFile(<original>); Bitmap bm=new Bitmap(thumbXsize, thumbYsize); Graphics g=Graphics.FromImage(bm); g.InterpolationMode=InterpolationMode.HighQualityBilinear; g.DrawImage(i,new Rectangle(0,0,bm.Width,bm.Height),0,0,i.Width, i.Height,GraphicsUnit.pixel); g.Dispose(); i.Dispose(); bm now holds a thumbnail image that you can save or display; -- Bob Powell [MVP] Visual C#, System.Drawing Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "George Nevsky" <apokriffree@hotbox.ru> wrote in message news:%23iy686%235EHA.208@TK2MSFTNGP12.phx.gbl... > But Graphics.FromImage doesn't work with indexed color pictures ... > > > "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message > news:OCu3TN35EHA.1564@TK2MSFTNGP09.phx.gbl... > > Just create your thumbnail manually by creating an image the size of the > > desired thumbnail, obtaining a Graphics object from it using > > Graphics.FromImage and drawing the original image to the thumbnail at the > > appropriate size. > > > > -- > > Bob Powell [MVP] > > Visual C#, System.Drawing > > > > Find great Windows Forms articles in Windows Forms Tips and Tricks > > http://www.bobpowell.net/tipstricks.htm > > > > Answer those GDI+ questions with the GDI+ FAQ > > http://www.bobpowell.net/faqmain.htm > > > > All new articles provide code in C# and VB.NET. > > Subscribe to the RSS feeds provided and never miss a new article. > > > > > > > > > > > > "George Nevsky" <apokriffree@hotbox.ru> wrote in message > > news:ONYhvK35EHA.3124@TK2MSFTNGP11.phx.gbl... > >> I wish to use GetThumbnailImage method of Image object to downsize an > > image > >> but I don't want to use embedded thumbnail which can be in original image > >> file. > >> > >> > >> > >> I know probably it isn't best in the world way but I like it. It works > >> absolutely fine for my purposes. It is very simple. It works fine with > >> indexed color images like GIF as well as with true color images like > >> JPEG. > >> It is pretty fast. But it has one horrible thing. It is using embedded > >> thumbnail (if there is one) which can be ugly. > >> > >> How to tell to GDI+ don't use embedded thumbnail? > >> > >> > > > > > >
Have you tried resize indexed color image (GIF) with your function?
This line: [quoted text, click to view] > Dim g As Graphics = Graphics.FromImage(bmpNewBitmap) should generate exception "A Graphics object cannot be created from an image that has an indexed pixel format." [quoted text, click to view] "Rémy Samulski" <samulski@hotmail.com> wrote in message news:1103701069.808543.160590@f14g2000cwb.googlegroups.com... >I use the following code to create thumbnails and to enlarge images. > > Public Shared Function ResizeBitmap( _ > ByVal bmpBitmap As Bitmap, _ > ByVal snglBoundingWidth As Single, _ > ByVal snglBoundingHeight As Single, _ > Optional ByVal blnHighQuality As Boolean = False) As Bitmap > Dim snglNewWidth, snglNewHeight As Single > > If snglBoundingWidth > 1 And snglBoundingHeight > 1 Then > If (bmpBitmap.Height / bmpBitmap.Width) > > (snglBoundingHeight / snglBoundingWidth) Then > snglNewHeight = Int(snglBoundingHeight) > snglNewWidth = Int((bmpBitmap.Width / bmpBitmap.Height) > * snglNewHeight) > Else > snglNewWidth = Int(snglBoundingWidth) > snglNewHeight = Int((bmpBitmap.Height / > bmpBitmap.Width) * snglNewWidth) > End If > Else > snglNewWidth = bmpBitmap.Width * snglBoundingWidth > snglNewHeight = bmpBitmap.Height * snglBoundingHeight > End If > > Dim bmpNewBitmap As System.Drawing.Bitmap > > bmpNewBitmap = New Bitmap(bmpBitmap, snglNewWidth, > snglNewHeight) > > If blnHighQuality = True Then > Dim g As Graphics = Graphics.FromImage(bmpNewBitmap) > > g.InterpolationMode = > Drawing.Drawing2D.InterpolationMode.HighQualityBicubic > > g.DrawImage(bmpBitmap, 0, 0, bmpNewBitmap.Width, > bmpNewBitmap.Height) > End If > > Return bmpNewBitmap > End Function >
You cannot create a Graphics object from a GIF.
The resulting thumbnail will always be a high colour image best saved as a jpeg. -- Bob Powell [MVP] Visual C#, System.Drawing Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "George Nevsky" <apokriffree@hotbox.ru> wrote in message news:e6%23IVqF6EHA.4040@TK2MSFTNGP14.phx.gbl... > Ok. Thank you for this example but can you also help me with indexed color > image? > How to create Graphics object from GIF? > > "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message > news:ehU4OpB6EHA.3856@tk2msftngp13.phx.gbl... > > It's not the indexed image that you should use. > > > > Image i=Image.FromFile(<original>); > > Bitmap bm=new Bitmap(thumbXsize, thumbYsize); > > Graphics g=Graphics.FromImage(bm); > > g.InterpolationMode=InterpolationMode.HighQualityBilinear; > > g.DrawImage(i,new Rectangle(0,0,bm.Width,bm.Height),0,0,i.Width, > > i.Height,GraphicsUnit.pixel); > > g.Dispose(); > > i.Dispose(); > > > > bm now holds a thumbnail image that you can save or display; > > -- > > Bob Powell [MVP] > > Visual C#, System.Drawing > > > > Find great Windows Forms articles in Windows Forms Tips and Tricks > > http://www.bobpowell.net/tipstricks.htm > > > > Answer those GDI+ questions with the GDI+ FAQ > > http://www.bobpowell.net/faqmain.htm > > > > All new articles provide code in C# and VB.NET. > > Subscribe to the RSS feeds provided and never miss a new article. > > > > > > > > > > > > "George Nevsky" <apokriffree@hotbox.ru> wrote in message > > news:%23iy686%235EHA.208@TK2MSFTNGP12.phx.gbl... > >> But Graphics.FromImage doesn't work with indexed color pictures ... > >> > >> > >> "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message > >> news:OCu3TN35EHA.1564@TK2MSFTNGP09.phx.gbl... > >> > Just create your thumbnail manually by creating an image the size of > >> > the > >> > desired thumbnail, obtaining a Graphics object from it using > >> > Graphics.FromImage and drawing the original image to the thumbnail at > > the > >> > appropriate size. > >> > > >> > -- > >> > Bob Powell [MVP] > >> > Visual C#, System.Drawing > >> > > >> > Find great Windows Forms articles in Windows Forms Tips and Tricks > >> > http://www.bobpowell.net/tipstricks.htm > >> > > >> > Answer those GDI+ questions with the GDI+ FAQ > >> > http://www.bobpowell.net/faqmain.htm > >> > > >> > All new articles provide code in C# and VB.NET. > >> > Subscribe to the RSS feeds provided and never miss a new article. > >> > > >> > > >> > > >> > > >> > > >> > "George Nevsky" <apokriffree@hotbox.ru> wrote in message > >> > news:ONYhvK35EHA.3124@TK2MSFTNGP11.phx.gbl... > >> >> I wish to use GetThumbnailImage method of Image object to downsize an > >> > image > >> >> but I don't want to use embedded thumbnail which can be in original > > image > >> >> file. > >> >> > >> >> > >> >> > >> >> I know probably it isn't best in the world way but I like it. It works > >> >> absolutely fine for my purposes. It is very simple. It works fine with > >> >> indexed color images like GIF as well as with true color images like > >> >> JPEG. > >> >> It is pretty fast. But it has one horrible thing. It is using embedded > >> >> thumbnail (if there is one) which can be ugly. > >> >> > >> >> How to tell to GDI+ don't use embedded thumbnail? > >> >> > >> >> > >> > > >> > > >> > >> > > > > > >
You will see in both my example and Remy's that the bitmap for which the
Graphics object is obtained is a new high-colour bitmap. The bitmap creation in Remy's example might cause problems though. You should just use new Bitmap(snglNewWidth,snglNewHeight) -- Bob Powell [MVP] Visual C#, System.Drawing Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "George Nevsky" <apokriffree@hotbox.ru> wrote in message news:O6I8LXD6EHA.3944@TK2MSFTNGP12.phx.gbl... > Have you tried resize indexed color image (GIF) with your function? > This line: > > Dim g As Graphics = Graphics.FromImage(bmpNewBitmap) > should generate exception "A Graphics object cannot be created from an image > that has an indexed pixel format." > > > "Rémy Samulski" <samulski@hotmail.com> wrote in message > news:1103701069.808543.160590@f14g2000cwb.googlegroups.com... > >I use the following code to create thumbnails and to enlarge images. > > > > Public Shared Function ResizeBitmap( _ > > ByVal bmpBitmap As Bitmap, _ > > ByVal snglBoundingWidth As Single, _ > > ByVal snglBoundingHeight As Single, _ > > Optional ByVal blnHighQuality As Boolean = False) As Bitmap > > Dim snglNewWidth, snglNewHeight As Single > > > > If snglBoundingWidth > 1 And snglBoundingHeight > 1 Then > > If (bmpBitmap.Height / bmpBitmap.Width) > > > (snglBoundingHeight / snglBoundingWidth) Then > > snglNewHeight = Int(snglBoundingHeight) > > snglNewWidth = Int((bmpBitmap.Width / bmpBitmap.Height) > > * snglNewHeight) > > Else > > snglNewWidth = Int(snglBoundingWidth) > > snglNewHeight = Int((bmpBitmap.Height / > > bmpBitmap.Width) * snglNewWidth) > > End If > > Else > > snglNewWidth = bmpBitmap.Width * snglBoundingWidth > > snglNewHeight = bmpBitmap.Height * snglBoundingHeight > > End If > > > > Dim bmpNewBitmap As System.Drawing.Bitmap > > > > bmpNewBitmap = New Bitmap(bmpBitmap, snglNewWidth, > > snglNewHeight) > > > > If blnHighQuality = True Then > > Dim g As Graphics = Graphics.FromImage(bmpNewBitmap) > > > > g.InterpolationMode = > > Drawing.Drawing2D.InterpolationMode.HighQualityBicubic > > > > g.DrawImage(bmpBitmap, 0, 0, bmpNewBitmap.Width, > > bmpNewBitmap.Height) > > End If > > > > Return bmpNewBitmap > > End Function > > > >
Ok. Thank you for this example but can you also help me with indexed color
image? How to create Graphics object from GIF? [quoted text, click to view] "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message news:ehU4OpB6EHA.3856@tk2msftngp13.phx.gbl... > It's not the indexed image that you should use. > > Image i=Image.FromFile(<original>); > Bitmap bm=new Bitmap(thumbXsize, thumbYsize); > Graphics g=Graphics.FromImage(bm); > g.InterpolationMode=InterpolationMode.HighQualityBilinear; > g.DrawImage(i,new Rectangle(0,0,bm.Width,bm.Height),0,0,i.Width, > i.Height,GraphicsUnit.pixel); > g.Dispose(); > i.Dispose(); > > bm now holds a thumbnail image that you can save or display; > -- > Bob Powell [MVP] > Visual C#, System.Drawing > > Find great Windows Forms articles in Windows Forms Tips and Tricks > http://www.bobpowell.net/tipstricks.htm > > Answer those GDI+ questions with the GDI+ FAQ > http://www.bobpowell.net/faqmain.htm > > All new articles provide code in C# and VB.NET. > Subscribe to the RSS feeds provided and never miss a new article. > > > > > > "George Nevsky" <apokriffree@hotbox.ru> wrote in message > news:%23iy686%235EHA.208@TK2MSFTNGP12.phx.gbl... >> But Graphics.FromImage doesn't work with indexed color pictures ... >> >> >> "Bob Powell [MVP]" <bob@_spamkiller_bobpowell.net> wrote in message >> news:OCu3TN35EHA.1564@TK2MSFTNGP09.phx.gbl... >> > Just create your thumbnail manually by creating an image the size of >> > the >> > desired thumbnail, obtaining a Graphics object from it using >> > Graphics.FromImage and drawing the original image to the thumbnail at > the >> > appropriate size. >> > >> > -- >> > Bob Powell [MVP] >> > Visual C#, System.Drawing >> > >> > Find great Windows Forms articles in Windows Forms Tips and Tricks >> > http://www.bobpowell.net/tipstricks.htm >> > >> > Answer those GDI+ questions with the GDI+ FAQ >> > http://www.bobpowell.net/faqmain.htm >> > >> > All new articles provide code in C# and VB.NET. >> > Subscribe to the RSS feeds provided and never miss a new article. >> > >> > >> > >> > >> > >> > "George Nevsky" <apokriffree@hotbox.ru> wrote in message >> > news:ONYhvK35EHA.3124@TK2MSFTNGP11.phx.gbl... >> >> I wish to use GetThumbnailImage method of Image object to downsize an >> > image >> >> but I don't want to use embedded thumbnail which can be in original > image >> >> file. >> >> >> >> >> >> >> >> I know probably it isn't best in the world way but I like it. It works >> >> absolutely fine for my purposes. It is very simple. It works fine with >> >> indexed color images like GIF as well as with true color images like >> >> JPEG. >> >> It is pretty fast. But it has one horrible thing. It is using embedded >> >> thumbnail (if there is one) which can be ugly. >> >> >> >> How to tell to GDI+ don't use embedded thumbnail? >> >> >> >> >> > >> > >> >> > >
No problems resizing GIF's nor with the function I use in my example.
The only thing you should take into consideration is that the bitmap is resized without any anti-aliases when performing this code: ResizedBitmap = new Bitmap(OriginalBitmap, snglNewWidth, snglNewHeight) Furthermore my code is not speed optimised =) (as always). [quoted text, click to view] Bob Powell [MVP] wrote:
> The bitmap creation > in Remy's example might cause problems though. You should just use new > Bitmap(snglNewWidth,snglNewHeight)
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