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Pengantar Image Processing - Pendahuluan -

14 Januari 2011. Pengantar Image Processing - Pendahuluan -. Dr. Anto Satriyo Nugroho. Center for Information & Communication Technology, Agency for the Assessment & Application of Technology (PTIK-BPPT) Email: asnugroho@gmail.com URL: http://asnugroho.net. Persiapan Praktikum.

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Pengantar Image Processing - Pendahuluan -

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  1. 14 Januari 2011 Pengantar Image Processing- Pendahuluan - Dr. Anto Satriyo Nugroho Center for Information & Communication Technology, Agency for the Assessment & Application of Technology (PTIK-BPPT) Email: asnugroho@gmail.com URL: http://asnugroho.net

  2. Persiapan Praktikum • OS: Linux Ubuntu • Editor: vi, emacs, gedit • C Compiler: gcc • imagemagick • display • convert • xgraph

  3. Portable Gray Map • Isi sebuah PGM file adalah sbb. • A "magic number" for identifying the file type. A pgm image's magic number is the two characters "P5". • Whitespace (blanks, TABs, CRs, LFs). • A width, formatted as ASCII characters in decimal. • Whitespace. • A height, again in ASCII decimal. • Whitespace. • The maximum gray value (Maxval), again in ASCII decimal. Must be less than 65536, and more than zero. • A single whitespace character (usually a newline). • A raster of Height rows, in order from top to bottom. Each row consistsof Width gray values, in order from left to right. Each gray value is anumber from 0 through Maxval, with 0 being black and Maxval beingwhite. Each gray value is represented in pure binary by either 1 or 2 bytes. If the Maxval is less than 256, it is 1 byte. Otherwise, it is 2 bytes.The most significant byte is first. http://netpbm.sourceforge.net/doc/pgm.html

  4. Contoh: PGM file • Sebuah citra memiliki ukuran 4 kolom x 3 baris • Header (area yang berwarna hijau): terdiri dari 3 baris yang tertulis dalam plain text ASCII. Masing-masing adalah magick number (P5), lebar tinggi, dan nilai maksimum intensitas • Raster (area yang berwarna kuning): berisi data nilai intensitas masing-masing pixel dalam format BINARY. Dimulai dari pixel paling kiri atas menuju ke kanan bawah. “0” adalah hitam, sedangkan “255” adalah putih. P5 4 3 255 0 0 255 0 255 255 0 128 0 0 255 0

  5. Contoh membuat sebuah citra #include <stdio.h> #include <stdlib.h> main() { FILE *fp; int height=3, width=4; unsigned char putih=255, hitam=0, abu=128; fp=fopen(“contoh-1.pgm”,”w”); fprintf(fp,”P5\n%d %d\n255\n“,width,height); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&putih,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&putih,sizeof(unsigned char),1,fp); fwrite(&putih,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&abu,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fwrite(&putih,sizeof(unsigned char),1,fp); fwrite(&hitam,sizeof(unsigned char),1,fp); fclose(fp); }

  6. Bagaimana membaca sebuah citra ? #include <stdio.h> #include <stdlib.h> main() { FILE *fp; int i,j, height=3, width=4; char line[100]; unsigned char pixel_value; fp=fopen(“contoh-1.pgm”,”r”); fgets(line,100,fp); fgets(line,100,fp); fgets(line,100,fp); for(j=0;j<height;j++) for(i=0;i<width;i++) { fread(&pixel_value,sizeof(unsigned char),1,fp); printf(“baris ke %d kolom ke %d nilai pixel=%d\n”,j,i,pixel_value); } fclose(fp); }

  7. Latihan-1 Buatlah program untuk menampilkan citra: radius 25 tinggi 75 Lebar 100

  8. Latihan-2 Buatlah program untuk menampilkan nilai tiap pixel pada citra berikut (ukuran citra: 512x512)

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