Fifty Shades of Grey

Question

Boys and girls are excited to see Fifty Shades of Grey on the silver screen, we just want to code without being bothered, so here's a challenge to pick our brain.

You have to:

• Print on the screen fifty squares filled each with a different shade of grey
• If your language of choice lacks image processing capabilities, you could output an image file
• Squares must be visible, at least 20 x 20 pixels
• You cannot use random numbers unless you make sure each shade is unique.
• You cannot connect to any service over any network
• You cannot read any files in your program.
• You cannot use any libraries out of the standard libraries of your language of choice.

This is code golf so shortest code wins.

Answer 1

MATLAB, 24 bytes

Second attempt, now actually conforming to the rules.

imshow(0:1/49:1,'I',2e3)

The 'I' stands for 'InitialMagnification', but apparently Matlab will autocomplete names in name/value pairs. Sure is a good golfing trick!

Answer 2

Mathematica, 30 bytes

Here is another Mathematica approach:

ArrayPlot[#+5#2&~Array~{5,10}]

or

ArrayPlot[5#+#2&~Array~{10,5}]

The first one simply creates an array

{{6, 11, 16, 21, 26, 31, 36, 41, 46, 51}, 
 {7, 12, 17, 22, 27, 32, 37, 42, 47, 52}, 
 {8, 13, 18, 23, 28, 33, 38, 43, 48, 53}, 
 {9, 14, 19, 24, 29, 34, 39, 44, 49, 54}, 
 {10, 15, 20, 25, 30, 35, 40, 45, 50, 55}}

and the second one

{{6, 7, 8, 9, 10},
 {11, 12, 13, 14, 15},
 {16, 17, 18, 19, 20},
 {21, 22, 23, 24, 25},
 {26, 27, 28, 29, 30},
 {31, 32, 33, 34, 35},
 {36, 37, 38, 39, 40},
 {41, 42, 43, 44, 45},
 {46, 47, 48, 49, 50},
 {51, 52, 53, 54, 55}}

Then, ArrayPlot plots them as a grid and, by default, uses greyscale to visualise the values.

Answer 3

CJam - 23 (no actual graphical output)

Since CJam can't draw on the screen (yet?), I wrote a program that outputs an image in plain pgm format.
Save the output to a file called 50.pgm and open with an image viewer/editor.

"P2"1e3K51_,1>K*$K*~]N*

Try it online

The result looks like this:

Explanation:

"P2"     push "P2" (netpbm magic number)
1e3K     push 1000 and K=20 (image size)
51       push 51 (value of white)
_,       duplicate 51 and convert to an array [0 1 2 ... 50]
1>       remove 0 (slice from 1)
K*       repeat the array 20 times
$        sort, to get [(20 1's) (20 2's) ... (20 50's)]
K*       repeat the array 20 times
~        dump the elements on the stack
]        put everything from the stack in an array
N*       join with newlines

Answer 4

Mathematica 72 61 59 43 35 34 bytes

Current version (34 bytes)

GrayLevel[#/50]~Style~50 &~Array~50    

---

Earlier version (59 bytes), thanks to Martin Büttner.

Graphics[{GrayLevel[#/50],Cuboid@{#~Mod~9,#/9}}&/@Range@50]

Blue borders added to highlight position of squares.

Graphics[{EdgeForm[Blue], GrayLevel[#/50], Cuboid@{#~Mod~9, #/9}} & /@Range@50]

Number of squares:

    Length[%[[1]]]

50

---

First attempt (72 bytes)

If the squares can overlap. As Zgarb notes, there is a remote possibility that one square would hide another.

  Graphics@Table[{GrayLevel@k,Cuboid[{0,15}~RandomReal~2]},{k,.4,.89,.01}]

Answer 5

Sage - 26 24 35 29 characters

matrix(5,10,range(50)).plot()

It looks like this:

Previous attempts: First I had Matrix([range(50)]).plot(), then matrix_plot([range(50)]). These looked like this:

User @flawr pointed out that the squares produced with default settings are too small. Adding a figsize options fixes it, but it is 6 characters longer than the 5x10 version at the top of this answer:

matrix_plot([range(50)],figsize=20)

Answer 6

R, 47 42 39 38 37 36 35 bytes

Assuming they're allowed to overlap, this works. Symbols requires a vector that holds the size for each square, and I'm saving space by reusing the same vector for all function parameters. The largest square is always 1 inch wide. With 50:99 as the range of integers, the smallest square will be around half an inch wide, so 36 pixels at 72 dpi.

symbols(x,,,x<-50:99,bg=gray(x/99))

Thanks to everyone for the comments and suggestions, I'm pretty new to R so this is all very educational.

Previous versions:

symbols(x,sq=x<-50:99,bg=gray(x/99))            #36
x=50:99;symbols(x,sq=x,bg=gray(x/99))           #37
x<-50:99;symbols(x,sq=x,bg=gray(x/99))          #38
x<-1:50;symbols(x,sq=x/x,bg=gray(x/50))         #39
x<-1:50/50;symbols(x,sq=x/x,bg=rgb(x,x,x))      #42
x<-1:50/50;symbols(x,squares=x/x,bg=rgb(x,x,x)) #47

Previous image:

Answer 7

Java - 180

Pretty straightforward, just drawing boxes.

import java.awt.*;void f(){new Frame(){public void paint(Graphics g){for(int i=1;i<51;g.setColor(new Color(328965*i)),g.fillRect(i%8*20,i++/8*20,20,20))setSize(600,600);}}.show();}

With line breaks:

import java.awt.*;
    void f(){
        new Frame(){
            public void paint(Graphics g){
                for(int i=1;
                    i<51;
                    g.setColor(new Color(328965*i)),
                    g.fillRect(i%8*20,i++/8*20,20,20))
                    setSize(600,600);
            }
        }.show();
    }

Answer 8

ipython 2, 54 bytes

The best I could do was with an ipython program. Starting ipython with ipython -pylab and executing this program will show a graph with 50 shades of grey in 50 squares:

t=arange(50);c=t/50.;scatter(t%5,t,500,zip(c,c,c),'s')

Output:

Solution 2:

Here is another program (61 bytes):

imshow(arange(50).reshape(5,10)*.02,'Greys',None,1,'nearest')

that displays the following window:

Answer 9

BBC BASIC, 57

FORn=51TO2STEP-1VDU19;-1,n,n,n:RECTANGLEFILL0,0,n*20NEXT

The squares have to be at least 20 pixels but there's nothing to say they have to be the same size, so I guess this qualifies.

It may be possible to shorten this by using more low-level VDU codes. But changing from this pattern to a less interesting one is unlikely to make it shorter.

Answer 10

JavaScript (72, 70, 67 bytes)

72: original (borrowing the clever ■ usage from Sphinxxx's answer):

for(i=90;i>40;)document.write('<font color=#'+i+i+i--+' size=7>&#9632;')

70: stealing shamelessly from Ismael Miguel (who deserves the votes), a shorter for loop and allowing the browser to correct for a lack of # proceeding the colour code...

for(i=60;--i>9;)document.write('<font color='+i+i+i+' size=7>&#9632;')

67 bytes (65 chars): swapping the entity for the unicode character:

for(i=60;--i>9;)document.write('<font color='+i+i+i+' size=7>■')

Answer 11

C++, 98 83 characters

Okay so, you are going to need a terminal emulator that supports true colors. For mac os there are the nightly builds of iTerm2, for example. For unix I believe konsole supports it. Here's a list, just in case: https://gist.github.com/XVilka/8346728#now-supporting-truecolor

Compile with g++ (\e is compiler dependent).

For the squares to have enough area, you will have to change your terminal font size.

#include <cstdio>
int main(){for(int i=51;i--;)printf("\e[48;2;%i;%i;%im ",i,i,i);}

Using C libraries instead of C++ allows for shaving some characters.

C, 61 58 characters

This is the same program but in C, which assumes untyped function declarations to return int, and which doesn't need includes for some of the standard library functions, like in this case, printf. Suggested by @cartographer. Three characters less thanks to @user3601420

main(i){for(i=51;i--;)printf("\e[48;2;%i;%i;%im ",i,i,i);}

Compiles with a couple of warnings (for assuming main's return type to be int and for implicitly including the declaration of printf).

Answer 12

Python 2, 125 115 104 bytes

from turtle import*
shape("square")
bk(500)
ht()
pu()
exec'color((xcor()/2e3+.5,)*3);stamp();fd(21);'*50

Sample output:

Good old turtle. This was the only method I could think of in Python which prints images to a screen using only the standard libraries.

The square turtle shape just happens to be 21 by 21, which is very convenient. This can be seen by digging through turtle.py:

"square" : Shape("polygon", ((10,-10), (10,10), (-10,10), (-10,-10)))

If you have a high res monitor or don't mind a few squares being off-screen, then this is 93 bytes:

from turtle import*
shape("square")
ht()
pu()
exec'color((xcor()/2e3,)*3);stamp();fd(21);'*50

---

Demo

(This demo uses Skulpt by adapting the snippet found here. It is only included to give an idea as to what the code does — I had to modify a few bits to get it working.)

function out(a){var b=document.getElementById("output");b.innerHTML+=a}function builtinRead(a){if(void 0===Sk.builtinFiles||void 0===Sk.builtinFiles.files[a])throw"File not found: '"+a+"'";return Sk.builtinFiles.files[a]}
$(document).ready(function run(){Sk.canvas="canvas";Sk.configure({output:out,read:builtinRead});try{Sk.importMainWithBody("<stdin>",!1,'import turtle\nt=turtle.Turtle()\nt.speed(9)\nt.shape("square")\n\nt.bk(500)\nt.ht()\nt.pu()\nfor i in range(50):t.color(64+2*i,64+2*i,64+2*i);t.stamp();t.fd(21)')}catch(a){throw Error(a.toString());}})

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script><script src="http://www.skulpt.org/static/skulpt.min.js" type="text/javascript"></script><script src="http://www.skulpt.org/static/skulpt-stdlib.js" type="text/javascript"></script>
<canvas height="100" width="1200" id="canvas" style="border:1px solid gray">Your browser does not support HTML5 Canvas!</canvas>

Answer 13

J (43 41 40 38 33 29 characters)

After suggestions from randomra.

1!:2&4'P2 ',":(,*:,],*:#?~)50

This solution does not display anything as the standard library of J does not contain GUI routines. Instead, I generate an image and write it to standard output. The output is randomized, it ensured that all shades are distinct. Here is a some sample output and the image converted to png and rotated by 90° for easier viewing:

Answer 14

Excel vba, 81

In the immediate window:

for i=1 to 9:for j=1 to 9:k=i+j*10:cells(i,j).interior.color=rgb(k,k,k):next:next

on the active sheet:

^{{81 shades is just as much code as 50}}

Answer 15

Matlab 35 thanks to sanchises

imshow(int8(ones(20,1)*(0:.05:51)))

Matlab 36

imshow(uint8(ones(20,1)*(0:.05:51)))

Displays 50 squares filled with gray values 1 to 50 and 2 additional rectangles filled with gray value 0 and 51:

Matlab, 45

imshow(uint8(ones(20,1)*floor(1:0.05:50.95)))

Answer 16

R, 37 32 characters¹:

image(t(1:50),c=gray.colors(50))

However, the display for this looks … meh (image rotated 90° to fit better into text; compressed, original square side length > 20px):

Here’s a nicer version which plots the squares in random order inside a matrix (50 characters):

image(matrix(sample(1:50),10),c=gray.colors(50))

(And yes, the three adjacent squares of seemingly identical colours are actually three different shades of grey.)

¹ Yes, another R answer, and not even the shortest (now the shortest for R) – apologies. I was missing a pretty rendering in R.

Answer 17

JavaScript, 87 90 bytes

for(i=90;i>40;)document.write('<p style=background:#'+i+i+i--+';height:9ex;width:9ex>')

This outputs squares to the HTML, because it is really JavaScript's only method of graphical output. Thanks to edc65 for shaving off 3 bytes.

Answer 18

PHP, 96 88 74 bytes

Thanks to Ismael Miguel for saving 22 bytes!

for($i=60;--$i>9;)echo"<p style=background:#$i$i$i;height:9mm;width:9mm>";

Writes 50 <p>s with 9mm as height and width (which should be bigger than 20px on the majority of screens), stacked on each other, all with a minor difference in shade.

Generated result (the image is zoomed out and 90° rotated):

Answer 19

Javascript (77 71 bytes):

This answer is no longer IE11 based. It works because the browser converts the bad color codes into usable ones (by adding # to the number).

Here is the code:

for(i=59;i-->9;)document.write("<hr color="+i+i+i+" size=20 width=20>")

Firefox still has the quirk of making circles.

(Small edit: Changed for(i=61;i-->9;) to for(i=59;i-->9;) because it was producing 52 squares)

---

Old answer:

This is based on my PHP answer, and uses almost the same ways to make the squares:

for(i=51;i--;)document.write("<hr color=rgb("+[i,i,i]+") size=20 width=20>");

Not the shortest answer, but it's worth adding here.

---

This solution isn't compatible with Chrome (produces multiple green colors) and Firefox (same result, but produces circles? o.O WTH?)

Since this is code-golf, a solution working with a specific version or a specific software is acceptable.

Answer 20

Matlab - 33 bytes

surf(meshgrid(1:7)),colormap gray

Despite the verbose commands, the result is still quite compact. It looks a bit better if you replace surf with surface but that costs 3 chars.

If you don't notice the 50th gray square that is because it is a bit bigger than the others!

Answer 21

Piet- 2*103 = 206

This is unique in that the source code and the output fulfill the challenge:

Most of it is decorative, so I only counted the top two rows, which stand alone just fine. Outputs a grayscale ppm like some others have done.

Answer 22

JavaScript - 70 bytes

for(i=51;i-=1;)document.write('<a style=opacity:'+i/50+'>&#9632;</a>')

Answer 23

PHP (62 60 63 72 71 62 59 bytes):

I've made the shortest I could find:

for($i=59;$i-->9;)echo"<hr color=$i$i$i size=20 width=20>";

This is exactly the same code as my Javascript answer (with 71 bytes).

But SO MUCH shorter!

This have a quirk in Firefox: instead of squares, Firefox makes circles! (Go insanity!)
Othen than that, all the browsers produce the right color (even with the missing # on the color attribute).

---

Invalid submits and changelog:

Old answer, with 62 bytes.

while($i++<51)echo"<hr color=rgb($i,$i,$i) size=20 width=20>";

All shades are perfectly aligned.

This solution won't work for Chrome (will produce squares with multiple colors) and Firefox (which makes circles o.O Yes, circles with <hr>! Horizontal ruler is a circle on Firefox!).
You can test it on IE11 and it should be fine.

---

(simply removed from above)

I've noticed something awful: It was outputting #111 instead of #010101 for some colors.

This meant that some colors were repeating.

Therefore, I had to sacrifice a few bytes:

<?while(f>$c=dechex(65-$i++))echo"<hr color=#$c$c$c size=20 width=20>";

Outputs the 50 shades in perfect order, from lighter to darker.

Due to a correct point made by @edc65, I had to add width=20, to produce perfect squares.

Reduced one more byte by replacing f!=$c with f>$c, which works perfectly.

---

Final version, without width=20:

<?while(f!=$c=dechex(65-$i++))echo"<hr color=#$c$c$c size=20>";

This is invalid because it is required to output squares.
This outputs the shades from lighter to darker.

---

Reduced 1 byte by switching to a while loop, like this:

<?while($c=dechex(50-$i++))echo"<hr color=#$c$c$c size=20>";

First solution:

<?for($i=50;$c=dechex($i--);)echo"<hr color=#$c$c$c size=20>";

This doesn't have the shades neatly ordered, but there are 50 different ones.

There is nothing stating that they must be ordered, but there is a requirement on size.

I hope I can reduce it a lot more.

You can test it on http://writecodeonline.com/php/ (click on "Display as HTML").

Answer 24

Processing, 66 characters:

size(1000,20);for(int i=0;i<981;i+=20){fill(i/4);rect(i,0,20,20);}

Answer 25

CSS (87 chars)

Uses animation ;)

:after{content:'\25A0';font:9em z;animation:g 8s steps(50)}@keyframes g{to{color:#fff}}

The runnable version is longer since Webkit still needs the vendor prefix. :(

:after{content:'\25A0';font:9em z;-webkit-animation:g 8s steps(50);animation:g 8s steps(50)}@-webkit-keyframes g{to{color:#fff}}@keyframes g{to{color:#fff}}

If we're allowed a random, empty <a> element, we can get it down to just 72 characters:

a{padding:3em;animation:g 8s steps(50)}@keyframes g{to{background:#000}}

See? CSS is a legit programming language!

Answer 26

PostScript, 34 bytes

In ISO-Latin-1 encoding:

20’›‡üˆì0{’81e3’6’–10’k0ˆ                   (note, this is a Line Feed)
’c’§}’H

This is the binary equivalent to:

20 setlinewidth 1020 -20 0 { dup 1e3 div setgray 10 moveto 0 10 lineto stroke } for

(This assumes that you are using it on a device that is at least 1000 points [= 10 inches = 25.4 cm] wide.)

Answer 27

R, 36 bytes

I can make freekvd's answer shorter trivially.

x=9:59/59;symbols(x,sq=x,bg=gray(x))

(Sorry for not making a comment under his solution. Stackexchange does not allow me to make comments, vote etc yet).

Answer 28

C# - 173

Using LINQPAD

var b=new Bitmap(1000,20);var g=Graphics.FromImage(b);for(int i=0;i<50;i++)g.FillRectangle(new SolidBrush(Color.FromArgb(i*5,i*5,i*5)),new Rectangle(i*20,0,20,20));b.Dump();

Expanded:

var b = new Bitmap(1000, 20);
var g = Graphics.FromImage(b);
for (int i = 0; i < 50; i++)
    g.FillRectangle(new SolidBrush(Color.FromArgb(i * 5, i * 5, i * 5)), new Rectangle(i * 20, 0, 20, 20));
b.Dump();

Output:

Answer 29

DrRacket - 83

Just for the sake of firing up DrRacket 1 year after "Introduction to Systematic Program Design".

EDIT:

(require htdp/image)(map(λ(i)(rectangle 50 50'solid(make-color i i i)))(range 50))

Answer 30

JavaScript, 152 bytes.

Okay, so maybe this isn't the best solution but here is mine.

function b(a){c=document
e=c.createElement('p')
with(e.style){background="rgb("+[a,a,a]+")"
width=height="20px"}c.body.appendChild(e)
a<245&&b(a+5)}b(0)

Here is the output with css float left (just so it is easier to count the squares) and without:

Answer 31

R 45 42 characters

New version, after some comments (thanks!):

plot(1:50%%5,col=gray(1:50/60),ce=5,pc=15)

Old version

It generates an error, but works fine :)

plot(x<-1:50,x%%5,col=gray(x/60),lw=30,pc=22)

Answer 32

C++ Win32: 141 chars and 171 chars

C++ 171 chars

#include"stdafx.h"#include<windows.h>int _tmain(){HDC h=GetDC(0);for(int i=0;i<50;i++){SelectObject(h,CreatePen(0,9,RGB(64+i,64+i,64)));Rectangle(h,i*9,i*9,i*9+9,i*9+9);}}

This draws 50 grey boxes to your desktop.

Which is super long, but pretty good for actually drawing squares in C++. I doesn't think I was ever going to win/not-come-last but I'm pretty satisfied with this. I can't guarantee the whole pixel thing as I use coordinates, but IWOMM :D.

I don't know if win32 counts as a standard library of c++, but I was more interested in the win32 than the c++ tbh. I had a crack at GDI, which look prettier but is super verbose. I was hoping I could get a win32 ColorChooser and turn them all grey for instant victory, but alas no.

Here's the idea (I've removed the resource leak from this extended version):

#include "stdafx.h"
#include <windows.h>
int _tmain(int a, _TCHAR* b[])
{
   HDC h=GetWindowDC(GetDesktopWindow()); //Zero works for GetDesktopWindow() as  Konrad Rudolph points out. GetDC is a good as GetWindowDC.
   for (int i = 0; i < 50; i++){
       HPEN p = CreatePen(PS_COSMETIC, 9, RGB(64 + i, 64 + i, 64)); //PS_COSMETIC is 0
       SelectObject(h, p); MoveToEx(h, 0, 0, NULL); //We can get away with removing MoveToEx and assuming it starts in the top left
       Rectangle(h, i * 9, i * 9, i * 9 + 9, i * 9 + 9); DeleteObject(p);
   }
   DeleteDC(h); //Or was it releaseDC? Who cares. The golf'd code leaks it anyway.
}

Also this can happen. When you want to get rid of it you just 'wipe' it away with another window. You would also not believe how slow this is to execute.

Konrad Rudolph's comment: C++ 141

// stdafx.h isn’t needed.
// However, we DO need the line break after the include,
// even in the golf version.
#include <windows.h>
// _tmain => main; VC++ accepts both.
int main()
{
   HDC h = GetDC(0);
  // Remove i++ here …
  for (int i = 0; i < 50;){
  // 65793 == 0x010101; multiplying with 1…50 generates
  // grey tones and is much shorter than RGB macro use
  SelectObject(h, CreatePen(0, 9, i*65793));
  // i * 9 + 9 == i * 10
  // … add i++ here.
  Rectangle(h, i * 9, i * 9, i * 10, i++ * 10);
  }
}

short.cpp

#include <windows.h>
int main(){HDC h=GetDC(0);for(int i=0;i<50;){SelectObject(h,CreatePen(0,9,i*65793));Rectangle(h,i*9,i*9,i*10,i++*10);}}
//141 with the line break

Answer 33

Pyth - 23 21 bytes

Is similar to CJam solution. Outputs is PGM format, save output as foo.pgm and view here. Edited it to make it conform to PGM specs so that lines are less than 70 chars long, in fact they are only one pixel long.

K50"P2"*KKKKVKjbS*UKK

Generates: Is fifty fifty by fifty squares. Goes from black to 49/50 of the way to white.

K50             K=50
"P2"            Prints P2 or pgm header magic #
*KK             Prints the length: 50*50
K               Prints width: 50
K               Prints value of white: 50
V         K     Do 50 times to make height of square 50
 j              joins by
  b             linebreaks
   S            Sort to bring out make each shade consecutive
    *  K        Times 50 to make length 50
     UK         Unary range 50 (0-49)

Answer 34

R - 35 characters

Barplot uses gray.colors by default, helpful to save some bytes. To make sure the size is sufficient regardless of the screen size, the window size has to be defined beforehand, with x and y size picked as to generate a 1:1 aspect ratio.

x11(,1.7,23);barplot(matrix(1,50))

Output, rotated 90° and sized down:

As per comments below, the x11() results vary between machines. Hence, a safer option - also forcing aspect ratio of 1 - is dev.new. Run from terminal:

dev.new(height=20);barplot(matrix(1,50),as=1) 

That's 46 characters. If manual resizing is allowed, barplot(matrix(1,50),as=1) is enough - only 27 characters.

Answer 35

HTML/CSS - 81 characters

This is a very borderline solution because the shades aren't displayed very accurately (Chrome and Firefox both just use dithering), but in theory it "should" display 50 distinct shades. Also, the code is probably not very W3C compliant, but it compiles on any browser that knows CSS3.

<div style="height:1000px;width:20px;background:linear-gradient(#000,#303030);"/>

Note that 0x30 is 50 and 1000 is 50*20.

Answer 36

C (73 65 characters)

Outputs a binary PGM to stdout, 20x20 squares.

s;main(){puts("P5 1000 20 50");while(s<2e4)putchar(s++%1000/20);}

Moar tricks would have been possible with 2^n instead of 50 shades, but nevermind.

Answer 37

CoffeeScript, 86 bytes

As per edc56's comment on the JavaScript solution:

i=90;document.write '<p style=background:#'+i+i+i--+';height:1em;width:1em>'while i>40

Answer 38

Python 2, 78 characters

This prints an image in PGM format to standard output (I took the idea from aditsu's CJam answer):

print"P2 2500 50 51"
r=range(50)
for x in r:
 for y in r:
  for z in r:print y

I wish Python would let me put all 3 fors on the same line. At least it lets me use a single space (or single tab) for each indentation level. I tried using variants of for t in itertools.product(r,r,r) instead, but the import is long and kills the benefit.

Answer 39

Mathematica, 20 characters

ArrayPlot@{Range@50}

gives the following output:

Answer 40

A basic javaScript code is given by:

<script>
"use strict";
var Div=null;
window.onload=function ()
{
 Div=document.getElementsByTagName("div")[0];
 var c=150,n=0,p=null;
 do {
     p=document.createElement("p");
     p.style.backgroundColor="rgb(" + c + "," + c + "," + c + ")";
     Div.appendChild(p);
     if ( ++n<50 ) c+=2; else break;
 } while ( true );
};
</script>

Answer 41

Haskell 133

import Data.List
r=replicate 20
f 0=""
f i=(f(i-1))++(concat$r$'\n':(intercalate " "$r$show i))
main=putStr $"P2\n20 1000\n50"++f 50

outputs in Netpbm Format to stdout

Answer 42

FFmpeg, 61 bytes

ffplay -f lavfi color=s=1000x20,format=y8,geq=8+4*trunc(X/20)

Answer 43

Excel VBA, 60 Bytes

Anonymous VBE immediate window function that takes no input and outputs to the range [A1:A50] on the ActiveSheet object

For i=1To 50:j=5*i:Cells(i,1).Interior.Color=RGB(j,j,j):Next

Answer 44

Javascript (60 char)

for(i=51;i--;)document.write("<hr color="+i+i+i+" size=20>")

Answer 45

Python, 72 bytes

print'P2 1000 20 50 '+20*(''.join([20*(str(x)+' ')for x in range(50)]))

Another PPM answer, usage:

python golf_grey.py > grey.ppm