Bitmap/Read a PPM file: Difference between revisions
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=={{header|D}}== |
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This example uses storage defined on [[Basic bitmap storage]] problem page. |
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This is wrap-around defined storage, P6 binary mode. |
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{{Works with|tango}} |
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<lang D> |
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import tango.core.Exception; |
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import tango.io.FileConduit; |
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import tango.io.MappedBuffer; |
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import tango.io.stream.LineStream; |
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import tango.io.stream.DataStream; |
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import tango.io.protocol.Reader; |
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import tango.text.convert.Integer; |
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class P6Image { |
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class BadInputException : Exception { this() { super("Bad file format"); } } |
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class NoImageException : Exception { this() { super("No image data"); } } |
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static const char[] type = "P6"; |
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MappedBuffer fileBuf; |
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ubyte _maxVal, gotImg; |
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public: |
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RgbBitmap bitmap; |
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this (FileConduit input) { |
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fileBuf = new MappedBuffer(input); |
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if (processHeader(new LineInput(fileBuf))) |
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throw new BadInputException; |
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if (processData(new DataInput(fileBuf))) |
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throw new BadInputException; |
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} |
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ubyte maxVal() { return _maxVal; } |
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int processHeader(LineInput li) { |
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char[] line; |
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uint eaten; |
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li.readln(line); |
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if (line != type) return 1; |
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li.readln(line); |
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// skip comment lines |
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while (line.length && line[0] == '#') li.readln(line); |
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auto width = parse(line, 0, &eaten); |
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auto height = parse(line[eaten..$], 0, &eaten); |
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if (!eaten || width > 0xffff_ffff || height > 0xffff_ffff) return 1; |
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li.readln(line); |
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auto temp = parse(line, 0, &eaten); |
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if (!eaten || temp > 255) return 1; |
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_maxVal = temp; |
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bitmap = RgbBitmap(width, height); |
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gotImg = 1; |
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return 0; |
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} |
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int processData(DataInput di) { |
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if (! gotImg) throw new NoImageException; |
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foreach (ref cell; bitmap) { |
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cell(di.getByte, di.getByte, di.getByte); |
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} |
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return 0; |
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} |
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} |
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</lang> |
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Reading from file: |
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<lang> |
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auto p6 = new P6Image(new FileConduit("image.ppm")); |
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</lang> |
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=={{header|Forth}}== |
=={{header|Forth}}== |
Revision as of 01:07, 29 March 2009
You are encouraged to solve this task according to the task description, using any language you may know.
Using the data storage type defined on this page for raster images, read an image from a PPM file (binary P6 prefered). (Read the definition of PPM file on Wikipedia.)
Task: Use write ppm file solution and grayscale image solution with this one in order to convert a color image to grayscale one.
Ada
<lang ada> with Ada.Characters.Latin_1; use Ada.Characters.Latin_1; with Ada.Integer_Text_IO; use Ada.Integer_Text_IO; with Ada.Streams.Stream_IO; use Ada.Streams.Stream_IO;
function Get_PPM (File : File_Type) return Image is
use Ada.Characters.Latin_1; use Ada.Integer_Text_IO;
function Get_Line return String is -- Skips comments Byte : Character; Buffer : String (1..80); begin loop for I in Buffer'Range loop Character'Read (Stream (File), Byte); if Byte = LF then exit when Buffer (1) = '#'; return Buffer (1..I - 1); end if; Buffer (I) := Byte; end loop; if Buffer (1) /= '#' then raise Data_Error; end if; end loop; end Get_Line;
Height : Integer; Width : Integer;
begin
if Get_Line /= "P6" then raise Data_Error; end if; declare Line : String := Get_Line; Start : Integer := Line'First; Last : Positive; begin Get (Line, Width, Last); Start := Start + Last; Get (Line (Start..Line'Last), Height, Last); Start := Start + Last; if Start <= Line'Last then raise Data_Error; end if; if Width < 1 or else Height < 1 then raise Data_Error; end if; end; if Get_Line /= "255" then raise Data_Error; end if; declare Result : Image (1..Height, 1..Width); Buffer : String (1..Width * 3); Index : Positive; begin for I in Result'Range (1) loop String'Read (Stream (File), Buffer); Index := Buffer'First; for J in Result'Range (2) loop Result (I, J) := ( R => Luminance (Character'Pos (Buffer (Index))), G => Luminance (Character'Pos (Buffer (Index + 1))), B => Luminance (Character'Pos (Buffer (Index + 2))) ); Index := Index + 3; end loop; end loop; return Result; end;
end Get_PPM; </lang> The implementation propagates Data_Error when the file format is incorrect. End_Error is propagated when the file end is prematurely met. The following example illustrates conversion of a color file to grayscale. <lang ada> declare
F1, F2 : File_Type;
begin
Open (F1, In_File, "city.ppm"); Create (F2, Out_File, "city_grayscale.ppm"); Put_PPM (F2, Color (Grayscale (Get_PPM (F1)))); Close (F1); Close (F2);
end; </lang>
C
It is up to the caller to open the file and pass the handler to the function. So this code can be used in Read image file through a pipe without modification. It only understand the P6 file format.
Interface:
<lang c>image get_ppm(FILE *pf);</lang>
Implementation:
<lang c>#include "imglib.h"
- define PPMREADBUFLEN 256
image get_ppm(FILE *pf) {
char buf[PPMREADBUFLEN], *t; image img; unsigned int w, h, d; int r; if (pf == NULL) return NULL; t = fgets(buf, PPMREADBUFLEN, pf); if ( (t == NULL) || ( strncmp(buf, "P6\n", 3) != 0 ) ) return NULL; do { /* Px formats can have # comments after first line */ t = fgets(buf, PPMREADBUFLEN, pf); if ( t == NULL ) return NULL; } while ( strncmp(buf, "#", 1) == 0 ); r = sscanf(buf, "%u %u", &w, &h); if ( r < 2 ) return NULL; r = fscanf(pf, "%u\n", &d); if ( (r < 1) || ( d != 255 ) ) return NULL; img = alloc_img(w, h); if ( img != NULL ) { size_t rd = fread(img->buf, sizeof(pixel), w*h, pf); if ( rd < w*h ) { free_img(img); return NULL; } return img; }
}</lang>
The following acts as a filter to convert a PPM file read from standard input into a PPM gray image, and it outputs the converted image to standard output (see Grayscale image, Write ppm file, and Raster graphics operations in general):
<lang c>#include <stdio.h>
- include "imglib.h"
int main() {
image source; grayimage idest; source = get_ppm(stdin); idest = tograyscale(source); free_img(source); source = tocolor(idest); output_ppm(stdout, source); free_img(source); free_img((image)idest); return 0;
}</lang>
D
This example uses storage defined on Basic bitmap storage problem page.
This is wrap-around defined storage, P6 binary mode.
<lang D> import tango.core.Exception; import tango.io.FileConduit; import tango.io.MappedBuffer; import tango.io.stream.LineStream; import tango.io.stream.DataStream; import tango.io.protocol.Reader; import tango.text.convert.Integer;
class P6Image {
class BadInputException : Exception { this() { super("Bad file format"); } } class NoImageException : Exception { this() { super("No image data"); } } static const char[] type = "P6"; MappedBuffer fileBuf; ubyte _maxVal, gotImg;
public:
RgbBitmap bitmap;
this (FileConduit input) { fileBuf = new MappedBuffer(input); if (processHeader(new LineInput(fileBuf))) throw new BadInputException;
if (processData(new DataInput(fileBuf))) throw new BadInputException; }
ubyte maxVal() { return _maxVal; }
int processHeader(LineInput li) { char[] line; uint eaten;
li.readln(line); if (line != type) return 1;
li.readln(line); // skip comment lines while (line.length && line[0] == '#') li.readln(line); auto width = parse(line, 0, &eaten); auto height = parse(line[eaten..$], 0, &eaten); if (!eaten || width > 0xffff_ffff || height > 0xffff_ffff) return 1;
li.readln(line); auto temp = parse(line, 0, &eaten); if (!eaten || temp > 255) return 1; _maxVal = temp;
bitmap = RgbBitmap(width, height);
gotImg = 1; return 0; }
int processData(DataInput di) { if (! gotImg) throw new NoImageException; foreach (ref cell; bitmap) { cell(di.getByte, di.getByte, di.getByte); } return 0; }
} </lang>
Reading from file: <lang> auto p6 = new P6Image(new FileConduit("image.ppm")); </lang>
Forth
: read-ppm { fid -- bmp } pad dup 80 fid read-line throw 0= abort" Partial line" s" P6" compare abort" Only P6 supported." pad dup 80 fid read-line throw 0= abort" Partial line" 0. 2swap >number 1 /string \ skip space 0. 2swap >number 2drop drop nip ( w h ) bitmap { bmp } pad dup 80 fid read-line throw 0= abort" Partial line" s" 255" compare abort" Only 8-bits per color channel supported" 0 pad ! bmp bdim 0 do dup 0 do pad 3 fid read-file throw 3 - abort" Not enough pixel data in file" pad @ i j bmp b! loop loop drop bmp ;
\ testing round-trip 4 3 bitmap value test red test bfill green 1 2 test b! s" red.ppm" w/o create-file throw test over write-ppm close-file throw s" red.ppm" r/o open-file throw dup read-ppm value test2 close-file throw : bsize ( bmp -- len ) bdim * pixels bdata ; test dup bsize test2 dup bsize compare . \ 0 if identical
Fortran
(This function is part of module RCImageIO, see Write ppm file)
<lang fortran> subroutine read_ppm(u, img)
integer, intent(in) :: u type(rgbimage), intent(out) :: img integer :: i, j, ncol, cc character(2) :: sign character :: ccode img%width = 0 img%height = 0 nullify(img%red) nullify(img%green) nullify(img%blue)
read(u, '(A2)') sign read(u, *) img%width, img%height read(u, *) ncol
write(0,*) sign write(0,*) img%width, img%height write(0,*) ncol
if ( ncol /= 255 ) return
call alloc_img(img, img%width, img%height)
if ( valid_image(img) ) then do j=1, img%height do i=1, img%width read(u, '(A1)', advance='no', iostat=status) ccode cc = iachar(ccode) img%red(i,j) = cc read(u, '(A1)', advance='no', iostat=status) ccode cc = iachar(ccode) img%green(i,j) = cc read(u, '(A1)', advance='no', iostat=status) ccode cc = iachar(ccode) img%blue(i,j) = cc end do end do end if
end subroutine read_ppm</lang>
Notes:
- doing formatted I/O with Fortran is a pain... And unformatted does not mean free; Fortran2003 has streams, but they are not implemented (yet) in GNU Fortran compiler. Here (as in the write part) I've tried to handle the PPM format through formatted I/O. The tests worked but I have not tried still everything.
- comments after the first line are not handled
Haskell
The definition of Bitmap.Netpbm.readNetpbm is given here. <lang haskell>import Bitmap import Bitmap.RGB import Bitmap.Gray import Bitmap.Netpbm
import Control.Monad import Control.Monad.ST
main =
(readNetpbm "original.ppm" :: IO (Image RealWorld RGB)) >>= stToIO . toGrayImage >>= writeNetpbm "new.pgm"</lang>
The above writes a PGM, not a PPM, since the image being output is in grayscale. If you actually want a gray PPM, convert the Image RealWorld Gray back to an Image RealWorld RGB first: <lang haskell>main =
(readNetpbm "original.ppm" :: IO (Image RealWorld RGB)) >>= stToIO . (toRGBImage <=< toGrayImage) >>= writeNetpbm "new.ppm"</lang>
OCaml
<lang ocaml>let read_ppm ~filename =
let ic = open_in filename in let line = input_line ic in if line <> "P6" then invalid_arg "not a P6 ppm file"; let line = input_line ic in let line = try if line.[0] = '#' (* skip comments *) then input_line ic else line with _ -> line in let width, height = Scanf.sscanf line "%d %d" (fun w h -> (w, h)) in let line = input_line ic in if line <> "255" then invalid_arg "not a 8 bit depth image"; let all_channels = let kind = Bigarray.int8_unsigned and layout = Bigarray.c_layout in Bigarray.Array3.create kind layout 3 width height in let r_channel = Bigarray.Array3.slice_left_2 all_channels 0 and g_channel = Bigarray.Array3.slice_left_2 all_channels 1 and b_channel = Bigarray.Array3.slice_left_2 all_channels 2 in for y = 0 to pred height do for x = 0 to pred width do r_channel.{x,y} <- (input_byte ic); g_channel.{x,y} <- (input_byte ic); b_channel.{x,y} <- (input_byte ic); done; done; close_in ic; (all_channels, r_channel, g_channel, b_channel)</lang>
and converting a given color file to grayscale: <lang ocaml>let () =
let img = read_ppm ~filename:"logo.ppm" in let img = to_color(to_grayscale ~img) in output_ppm ~oc:stdout ~img;
- </lang>
sending the result to stdout allows to see the result without creating a temporary file sending it through a pipe to the display utility of ImageMagick:
ocaml script.ml | display -
Perl
<lang perl>#! /usr/bin/perl
use strict; use Image::Imlib2;
my $img = Image::Imlib2->load("out0.ppm");
- let's do something with it now
$img->set_color(255, 255, 255, 255); $img->draw_line(0,0, $img->width,$img->height); $img->image_set_format("png"); $img->save("out1.png");
exit 0;</lang>
Vedit macro language
// Load a PPM file // @10 = filename // On return: // #10 points to buffer containing pixel data, // #11 = width, #12 = height. :LOAD_PPM: File_Open(@10) BOF Search("|X", ADVANCE) // skip "P6" #11 = Num_Eval(ADVANCE) // #11 = width Match("|X", ADVANCE) // skip separator #12 = Num_Eval(ADVANCE) // #12 = height Match("|X", ADVANCE) Search("|X", ADVANCE) // skip maxval (assume 255) Del_Block(0,CP) // remove the header Return
Example of usage. In addition to LOAD_PPM routine above, you need routine RGB_TO_GRAYSCALE from Grayscale image and routine SAVE_PPM from Write ppm file.
// Load RGB image Reg_Set(10, "|(USER_MACRO)\example.ppm") Call("LOAD_PPM") // Convert to grayscale #10 = Buf_Num Call("RGB_TO_GRAYSCALE") Buf_Switch(#10) Buf_Quit(OK) // Convert to RGB Call("GRAYSCALE_TO_RGB") // Save the image Reg_Set(10, "|(USER_MACRO)\example_gray.ppm") Call("SAVE_PPM") // Cleanup and exit Buf_Switch(#20) Buf_Quit(OK) return