Bitmap.Save with Encoder.Compression does not work...

[SKD]

Hello,

I have simple code snippet below (which is not very
different from the MSDN documentation for
Encoder.Compression (except for the image format which is
TIFF in the msdn example).
I am trying to load and paint a new image and then save
it in a new file. The original photoshop file is 1K. But
the output of this file is 12K. Please help if I am doing
something wrong here, in reducing the size of this file.
I have tried other enumerated values of Compression, but
12K is all I get always.

Thanks a lot in advance.

...........
Image iNew = Image.FromFile
("C:\\Work\\ImageConvert\\old.gif");
Bitmap bmNew = new Bitmap(iNew.Width, iNew.Height);
Graphics gNew = Graphics.FromImage(bmNew);
gNew.DrawImage(iNew, 0, 0, iNew.Width, iNew.Height);
EncoderParameters ep = new EncoderParameters(1);
ep.Param[0] = new EncoderParameter(new Encoder
(Encoder.Compression.Guid), (long)
EncoderValue.CompressionLZW);
bmNew.Save("C:\\Work\\ImageConvert\\new.gif", getCodecInfo
("image/gif"), ep);
.........

private ImageCodecInfo getCodecInfo(string mt)
{
ImageCodecInfo[] ici = ImageCodecInfo.GetImageEncoders();
int idx = 0;
for (int ii=0; ii<ici.Length; ii++)
{
if (ici[ii].MimeType == mt)
{
idx = ii;
break;
}
}
return ici[idx];
}

[John Hornick [MS]]

Hi,

You're using GIF, which doesn't support that encoder parameter. You
can use Bitmap.GetEncoderParameterList() to make this determination
programmatically.

There is a topic in the PSDK GDI+ documentation titled "Determining
the Parameters Supported by an Encoder" which describes this.

Thanks,
- John
Microsoft Developer Support
This posting is provided "AS IS" with no warranties, and confers no rights.
Visit http://www.microsoft.com/security for current information on security.

[SKD]

Hello John,

Thanks for the reply.
I tried this
EncoderParameters epNew = bmNew.GetEncoderParameterList
(ImageFormat.Gif.Guid);
It raises a file not found exception. It could be
something very stupid. If you can help, it will be great.

Thanks,
SKD.

[SKD]

Hi,

Now I did this

ImageCodecInfo[] ici = ImageCodecInfo.GetImageEncoders();

for (int ii=0; ii<ici.Length; ii++)
{

EncoderParameters epNew = null;
string mt = ici[ii].MimeType;
try
{
epNew = bmNew.GetEncoderParameterList(ici
[ii].Clsid);
if (mt == "image/jpeg")
{
bmNew.Save
("C:\\Work\\ImageConvert\\iNewJPG.jpg", ici[ii], epNew);
}
}
catch (Exception e1)
{
throw e1;
}
}

I find that out of all the four Params of epNew none of
them has the Guid of Encoder.Compression.Guid.

The GDI+ PSDK article talks about setting the compression
by changing the value of the EncoderQuality. But the
PointerValue member in C# is hidden because of protection
level. Please suggest a way other than re-writing my
entire code in C++.

Regards and Thanks.
SKD.

[John Hornick [MS]]

Hi,

> Now I did this
>
> ImageCodecInfo[] ici = ImageCodecInfo.GetImageEncoders();
> for (int ii=0; ii<ici.Length; ii++)
> {
> EncoderParameters epNew = null;
> string mt = ici[ii].MimeType;
> try
> {
> epNew = bmNew.GetEncoderParameterList(ici
> [ii].Clsid);
> if (mt == "image/jpeg")
> {
> bmNew.Save
> ("C:\\Work\\ImageConvert\\iNewJPG.jpg", ici[ii], epNew);
> }
> }
> catch (Exception e1)
> {
> throw e1;
> }
> }
>
> I find that out of all the four Params of epNew none of
> them has the Guid of Encoder.Compression.Guid.
>
> The GDI+ PSDK article talks about setting the compression
> by changing the value of the EncoderQuality. But the
> PointerValue member in C# is hidden because of protection
> level. Please suggest a way other than re-writing my
> entire code in C++.

private static ImageCodecInfo GetEncoderInfo(String mimeType)
{
int j;
ImageCodecInfo[] encoders;
encoders = ImageCodecInfo.GetImageEncoders();
for(j = 0; j < encoders.Length; ++j)
{
if(encoders[j].MimeType == mimeType)
return encoders[j];
}
return null;
}
private void SaveJPGWithCompressionSetting( Image image, string
szFileName, long lCompression )
{
EncoderParameters eps = new EncoderParameters(1);
eps.Param[0] = new EncoderParameter( Encoder.Quality, lCompression );
ImageCodecInfo ici = GetEncoderInfo("image/jpeg");
image.Save( szFileName, ici, eps );