You should be able to do something like this:

    using System.Drawing.Imaging;
    using System.Drawing;
    using System.IO;
    
    byte[] bitmap = GetYourImage();

    using(Image image = Image.FromStream(new MemoryStream(bitmap)))
    {
        image.Save(&quot;output.jpg&quot;, ImageFormat.Jpeg);  // Or Png
    }

Look [here][1] for more info.

Hopefully this helps.


  [1]: http://msdn.microsoft.com/en-us/library/9t4syfhh.aspx

I like Imagemagick.
http://www.imagemagick.org/script/api.php


There are two problems with this question:

Assuming you have a gray scale bitmap, you have two factors to consider:

1. For JPGS... what loss of quality is tolerable?
2. For pngs... what level of compression is tolerable?  (Although for most things I&#39;ve seen, you don&#39;t have that much of a choice, so this choice might be negligible.)  For anybody thinking this question doesn&#39;t make sense: yes, you can change the amount of compression/number of passes attempted to compress; check out either Ifranview or some of it&#39;s plugins.

Answer those questions, and then you might be able to find your original answer.



Is there a reason we include the `http` / `https` protocol on the `href` attribute of links?

Would it be fine to just leave it off:

    &lt;a href=&quot;example.com&quot;&gt;my site&lt;/a&gt;

html - links without http protocol

I see two different forms in Bash scripts which seem to do the same:

```lang-none
`some command`
```

and

```lang-none
$(some command)
```

What is the difference between the two, and when should I use each one of them?




What is the difference between backticks and $() in a Bash script?

I am currently working on an application that requires high-performance conversion of an unpadded byte array to either a PNG or JPEG. The image format doesn&#39;t matter, just as long as it&#39;s fast.

I have tried the .NET libraries and the performance is very bad. Can anyone recommend a good freeware library for this?

EDIT: the byte[] is an 8bit grayscale bitmap

Converting a byte array to PNG/JPG

I am currently working on an application that requires high-performance conversion of an unpadded byte array to either a PNG or JPEG. The image format doesn't matter, just as long as it's fast.
I have tried the .NET libraries and the performance is very bad. Can anyone recommend a good freeware library for this?
EDIT: the byte[] is an 8bit grayscale bitmap

I have a class that is `IComparable`:

    public class a : IComparable
    {
        public int Id { get; set; }
        public string Name { get; set; }
    
        public a(int id)
        {
            this.Id = id;
        }
    
        public int CompareTo(object obj)
        {
            return this.Id.CompareTo(((a)obj).Id);
        }
    }

When I add a list of object of this class to a hash set:

    a a1 = new a(1);
    a a2 = new a(2);
    HashSet&lt;a&gt; ha = new HashSet&lt;a&gt;();
    ha.add(a1);
    ha.add(a2);
    ha.add(a1);

Everything is fine and `ha.count` is `2`, but:

    a a1 = new a(1);
    a a2 = new a(2);
    HashSet&lt;a&gt; ha = new HashSet&lt;a&gt;();
    ha.add(a1);
    ha.add(a2);
    ha.add(new a(1));

Now `ha.count` is `3`.

 1. Why doesn&#39;t `HashSet` respect `a`&#39;s `CompareTo` method.
 2. Is `HashSet` the best way to have a list of unique objects?
    

How does HashSet compare elements for equality?

I&#39;ve been receiving an error on one of my pages that the linq query has timed out as it is taking too long.  It makes the page unusable.

It&#39;s a reports page which is only accessed by administrators around once a day.  It&#39;s unavoidable to trim this query down at all, it just has to sort through a lot of data.

Solutions to fix this I&#39;ve read are by increasing the timeout property in the data context, but I&#39;d like to avoid doing that as it would change it for the entire website.

Is there any way to set a larger time out for individual pages?

Linq-to-SQL Timeout

I&#39;m using entity framework to connect with the database. I&#39;ve one little problem:

I&#39;ve one table which have one varbinary(MAX) column(with filestream).

I&#39;m using SQL request to manage the &quot;Data&quot; part, but EF for the rest(metadata of the file).

I&#39;ve one code which has to get all files id, filename, guid, modification date, ... of a file. This doesn&#39;t need at all the &quot;Data&quot; field.

Is there a way to retrieve a List&lt;File&gt; but without this column filled?

Something like

    context.Files.Where(f=&gt;f.xyz).Exclude(f=&gt;f.Data).ToList();

??

I know I can create anonymous objects, but I need to transmit the result to a method, so no anonymous methods. And I don&#39;t want to put this in a list of anonymous type, and then create a list of my non-anonymous type(File).

The goal is to avoid this:
            
    using(RsSolutionsEntities context = new RsSolutionsEntities())
    {
        var file = context.Files
            .Where(f =&gt; f.Id == idFile)
            .Select(f =&gt; new {
                f.Id, f.MimeType, f.Size, f.FileName, f.DataType,
                f.DateModification, f.FileId
            }).FirstOrDefault();

        return new File() {
            DataType = file.DataType, DateModification = file.DateModification,
            FileId = file.FileId, FileName = file.FileName, Id = file.Id,
            MimeType = file.MimeType, Size = file.Size
        };
    }


(I&#39;m using here the anonymous type because otherwise you will get a NotSupportedException: The entity or complex type &#39;ProjectName.File&#39; cannot be constructed in a LINQ to Entities query.)

(e.g. this code throw the previous exception:

    File file2 = context.Files.Where(f =&gt; f.Id == idFile)
      .Select(f =&gt; new File() {Id = f.Id, DataType = f.DataType}).FirstOrDefault();

and &quot;File&quot; is the type I get with  a `context.Files.ToList()`. This is the good class: 

    using File = MyProjectNamespace.Common.Data.DataModel.File;

File is a known class of my EF datacontext:

    public ObjectSet&lt;File&gt; Files
    {
        get { return _files  ?? (_files = CreateObjectSet&lt;File&gt;(&quot;Files&quot;)); }
    }
    private ObjectSet&lt;File&gt; _files;

Retrieve an object from entityframework without ONE field

This code snippet works as expected for the `int` type:

    public class Test 
    {
        public int Value
        {
            get =&gt; _Value;
            set
            {
                if (_Value != value)
                    _Value = value;
            }
        }
        private int _Value;
    }

When `int` is replaced by the generic `T`, the compiler complains with:

&gt; Operator &#39;!=&#39; cannot be applied to operands of type &#39;T&#39; and &#39;T&#39;

Why does this happen and is there a way to solve it?

How to solve Operator &#39;!=&#39; cannot be applied to operands of type &#39;T&#39; and &#39;T&#39;

I have a method which returns different types of instances (classes):

    public [What Here?] GetAnything()
    {
         Hello hello = new Hello();
         Computer computer = new Computer();
         Radio radio = new Radio();

         return radio; or return computer; or return hello //should be possible?!      
    }



How can I do this and later work with the variables, e.g. `radio.Play()`, etc? 

Do I need to use generics, and if so, how?

C# Return different types?

When I click on an image link right now, Chrome downloads the image instead of opening it. 

Even if I right-click and select `Open link in new tab` Chrome *still* downloads the image, and I have to go through the extra steps of opening the file for viewing manually.

This feels like a mime-type issue to me, but why would Chrome not recognize &quot;image/png&quot; as a valid mime-type for viewing? All PNG images display just fine in an HTML page.

NOTE: This only happens for PNG images.

Chrome downloads PNG image links. I want them to open for viewing in a new tab. How do I make Chrome do that?

I found JPG does not support transparency, the alpha value is always 255. I am wondering only png supports transparency?

Only PNG supports transparency, is that true?

Suppose you have any image (PNG or JPG).
This image has a white background and I need to make this background transparent.

I have tried with these examples:

 - `convert original.png -background none transparent.png`
 - `convert original.png -background white -flatten -alpha off transparent.png`

but with no desirable results.

How can I make it?

IMPORTANT: Using `convert` command-line.

Set transparent background using ImageMagick and commandline prompt

I&#39;m using PIL to convert a transparent PNG image uploaded with Django to a JPG file. The output looks broken.

###Source file

![transparent source file][1]

###Code

    Image.open(object.logo.path).save(&#39;/tmp/output.jpg&#39;, &#39;JPEG&#39;)

or

    Image.open(object.logo.path).convert(&#39;RGB&#39;).save(&#39;/tmp/output.png&#39;)

###Result

Both ways, the resulting image looks like this:

![resulting file][2]

Is there a way to fix this? I&#39;d like to have white background where the transparent background used to be.


----------

# Solution

Thanks to the great answers, I&#39;ve come up with the following function collection:

    import Image
    import numpy as np


    def alpha_to_color(image, color=(255, 255, 255)):
        &quot;&quot;&quot;Set all fully transparent pixels of an RGBA image to the specified color.
        This is a very simple solution that might leave over some ugly edges, due
        to semi-transparent areas. You should use alpha_composite_with color instead.

        Source: http://stackoverflow.com/a/9166671/284318

        Keyword Arguments:
        image -- PIL RGBA Image object
        color -- Tuple r, g, b (default 255, 255, 255)

        &quot;&quot;&quot; 
        x = np.array(image)
        r, g, b, a = np.rollaxis(x, axis=-1)
        r[a == 0] = color[0]
        g[a == 0] = color[1]
        b[a == 0] = color[2] 
        x = np.dstack([r, g, b, a])
        return Image.fromarray(x, &#39;RGBA&#39;)


    def alpha_composite(front, back):
        &quot;&quot;&quot;Alpha composite two RGBA images.

        Source: http://stackoverflow.com/a/9166671/284318

        Keyword Arguments:
        front -- PIL RGBA Image object
        back -- PIL RGBA Image object

        &quot;&quot;&quot;
        front = np.asarray(front)
        back = np.asarray(back)
        result = np.empty(front.shape, dtype=&#39;float&#39;)
        alpha = np.index_exp[:, :, 3:]
        rgb = np.index_exp[:, :, :3]
        falpha = front[alpha] / 255.0
        balpha = back[alpha] / 255.0
        result[alpha] = falpha + balpha * (1 - falpha)
        old_setting = np.seterr(invalid=&#39;ignore&#39;)
        result[rgb] = (front[rgb] * falpha + back[rgb] * balpha * (1 - falpha)) / result[alpha]
        np.seterr(**old_setting)
        result[alpha] *= 255
        np.clip(result, 0, 255)
        # astype(&#39;uint8&#39;) maps np.nan and np.inf to 0
        result = result.astype(&#39;uint8&#39;)
        result = Image.fromarray(result, &#39;RGBA&#39;)
        return result


    def alpha_composite_with_color(image, color=(255, 255, 255)):
        &quot;&quot;&quot;Alpha composite an RGBA image with a single color image of the
        specified color and the same size as the original image.

        Keyword Arguments:
        image -- PIL RGBA Image object
        color -- Tuple r, g, b (default 255, 255, 255)

        &quot;&quot;&quot;
        back = Image.new(&#39;RGBA&#39;, size=image.size, color=color + (255,))
        return alpha_composite(image, back)

    
    def pure_pil_alpha_to_color_v1(image, color=(255, 255, 255)):
        &quot;&quot;&quot;Alpha composite an RGBA Image with a specified color.

        NOTE: This version is much slower than the
        alpha_composite_with_color solution. Use it only if
        numpy is not available.

        Source: http://stackoverflow.com/a/9168169/284318

        Keyword Arguments:
        image -- PIL RGBA Image object
        color -- Tuple r, g, b (default 255, 255, 255)

        &quot;&quot;&quot; 
        def blend_value(back, front, a):
            return (front * a + back * (255 - a)) / 255
        
        def blend_rgba(back, front):
            result = [blend_value(back[i], front[i], front[3]) for i in (0, 1, 2)]
            return tuple(result + [255])
        
        im = image.copy()  # don&#39;t edit the reference directly
        p = im.load()  # load pixel array
        for y in range(im.size[1]):
            for x in range(im.size[0]):
                p[x, y] = blend_rgba(color + (255,), p[x, y])
        
        return im

    def pure_pil_alpha_to_color_v2(image, color=(255, 255, 255)):
        &quot;&quot;&quot;Alpha composite an RGBA Image with a specified color.

        Simpler, faster version than the solutions above.

        Source: http://stackoverflow.com/a/9459208/284318

        Keyword Arguments:
        image -- PIL RGBA Image object
        color -- Tuple r, g, b (default 255, 255, 255)

        &quot;&quot;&quot;
        image.load()  # needed for split()
        background = Image.new(&#39;RGB&#39;, image.size, color)
        background.paste(image, mask=image.split()[3])  # 3 is the alpha channel
        return background


## Performance

The simple non-compositing `alpha_to_color` function is the fastest solution, but leaves behind ugly borders because it does not handle semi transparent areas.

Both the pure PIL and the numpy compositing solutions give great results, but `alpha_composite_with_color` is much faster (8.93 msec) than `pure_pil_alpha_to_color` (79.6 msec). &lt;del&gt;If numpy is available on your system, that&#39;s the way to go.&lt;/del&gt; (Update: The new pure PIL version is the fastest of all mentioned solutions.)

    $ python -m timeit &quot;import Image; from apps.front import utils; i = Image.open(u&#39;logo.png&#39;); i2 = utils.alpha_to_color(i)&quot;
    10 loops, best of 3: 4.67 msec per loop
    $ python -m timeit &quot;import Image; from apps.front import utils; i = Image.open(u&#39;logo.png&#39;); i2 = utils.alpha_composite_with_color(i)&quot;
    10 loops, best of 3: 8.93 msec per loop
    $ python -m timeit &quot;import Image; from apps.front import utils; i = Image.open(u&#39;logo.png&#39;); i2 = utils.pure_pil_alpha_to_color(i)&quot;
    10 loops, best of 3: 79.6 msec per loop
    $ python -m timeit &quot;import Image; from apps.front import utils; i = Image.open(u&#39;logo.png&#39;); i2 = utils.pure_pil_alpha_to_color_v2(i)&quot;
    10 loops, best of 3: 1.1 msec per loop


  [1]: http://i.stack.imgur.com/I2uNe.png
  [2]: http://i.stack.imgur.com/rmlPz.png

Convert RGBA PNG to RGB with PIL

I want to convert SVG images to PNG files with transparent background and anti-aliased edges (using semi-transparent pixels). Unfortunately I can&#39;t get ImageMagick to do the anti-aliasing, the edges always look terrible. Here&#39;s what I tried:

    convert +antialias -background transparent  in.svg -resize 25x25 out.png

Any ideas or a different command line tool I could use?

Convert SVG to transparent PNG with antialiasing, using ImageMagick

I was wondering if PNG contains data like the following?

What I did was to convert the jpg file to png format, and I was expecting to retrieve the same info I had on the jpg as below:

*Currently using this [as3 library][1] to read the data.*

- IDF0--- IDF @[134 - 248] (9 entries)
 - Orientation (SHORT) : 1 	
 - XResolution (RATIONAL) : 72/1 	
 - YResolution (RATIONAL) : 72/1
 - ResolutionUnit (SHORT) : 2 	
 - Software (ASCIIx16) : QuickTime 7.6.6 	
 - DateTime (ASCIIx20)  : 2011:10:02 22:43:37 	
 - HostComputer (ASCIIx16)  : Mac OS X 10.6.8
 - Exif IFD (LONG) : 8  34853	
 - GPS IFD (LONG) : 248

&amp;nbsp;

- EXIF IDF--- IDF @[8 - 134](10 entries)
 - ExifVersion (UNDEFINEDx4) : 0220
 - DateTimeOrigina (ASCIIx20)  : 2011:04:14 17:22:01
 - UserComment (UNDEFINEDx63)  : ASCII
 - FlashpixVersion (UNDEFINEDx4) : 0100
 - ColorSpace (SHORT) : 1
 - PixelXDimension (LONG) : 1022
 - PixelYDimension (LONG) : 486
 - Unknown (ASCIIx13)  : Image Tag-LOL
 - SceneCaptureType (SHORT) : 0

&amp;nbsp;

- GPS IDF--- IDF @[248 - 338](7 entries)
 - Interoperability Index (ASCIIx2) : N
 - Interoperability Version (RATIONALx3)  @425: 52/1, 1144/100, 0/1
 - Unknown (ASCIIx2) : W
 - Unknown (RATIONALx3)  : 1/1, 4392/100, 0/1
 - Unknown (RATIONAL)  : 5/1
 - Unknown (ASCIIx2) : T
 - Unknown (RATIONAL)  : 3694/117

&amp;nbsp;

  [1]: http://code.google.com/p/as3-xmp-file/

Does PNG contain EXIF data like JPG?

How can I use the Windows command line to change the extensions of thousands of files to `*****.jpg`?

Changing all files&#39; extensions in a folder with one command on Windows

I have the following:

    ghostscript-fonts-5.50-24
    ImageMagick-6.7.2-1
    ghostscript-9.02-1

Which I use to create a series of JPGs for each page using:

    convert -density 175 -colorspace sRGB test.pdf -resize 50% -quality 95 test.jpg

When I run this on my windows machine all appears to work ok, but on our linux server we get the black background problem.

The resulting JPGs have a black background rendering the image un-readable, what am I missing or is there something I should be doing to correct this?

I&#39;ve been all over google for days but each suggestion doesnt seem to work for me.

Any help is much appreciated, thanks in advance :)

**EDIT**

Just noticed this output when converting one of the PDFs that produces the black background:

    **** Warning: Fonts with Subtype = /TrueType should be embedded.
                 The following fonts were not embedded:
                        Arial
                        Arial,Bold
                        Arial,BoldItalic
    **** This file had errors that were repaired or ignored.
    **** The file was produced by:
    **** &gt;&gt;&gt;&gt; Microsoft&#171; Word 2010 &lt;&lt;&lt;&lt;
    **** Please notify the author of the software that produced this
    **** file that it does not conform to Adobe&#39;s published PDF
    **** specification.

This seems related but as we don&#39;t have control over how the PDFs are produced we need some way of fixing this server side.

Thanks again

Content Type	Original Author	Original Content on Stackoverflow
Question	user472875	View Question on Stackoverflow
Solution 1 - C#	Garrett Vlieger	View Answer on Stackoverflow
Solution 2 - C#	ahoffer	View Answer on Stackoverflow
Solution 3 - C#	JayC	View Answer on Stackoverflow

Converting a byte array to PNG/JPG

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

What is the difference between backticks and $() in a Bash script?

html - links without http protocol

Attributions