kuliah 02 - pengolahan citra digital sampling quantization 2

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Departemen Ilmu Komputer -IPB Pengantar Pengolahan Citra Digital

Kuliah 02 : Pembentukan Citra Digital (beberapa slide diambil dari catatan kuliah Richard Alan Peters)

Yeni Herdiyeni

Departemen Ilmu Komputer – IPB


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Image Formation

projection through lens

image of object

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Image Sensing and Acquisition

• Other (MRI (Magnetic Resonance Imaging), Ultrasound)

Single Sensor

Line Scan

Array Sensor

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Jenis Sensor

• CCD (Charge Couple Device)

• CMOS (Complementary Metal Oxide Semi Conductor)

• Infra Red

• X-Ray

• Radar

• MRI (Magnetic Resonance Imaging)

• Radio Telescope

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Departemen Ilmu Komputer -IPB Pengantar Pengolahan Citra Digital Fundamentals

CCD = Charge Couple Device

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Departemen Ilmu Komputer -IPB Pengantar Pengolahan Citra Digital Fundamentals

CCD = Charge Couple Device

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Persepsi Visual Manusia

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Citra : Fungsi Kontinyu

• Citra kontinyu diperoleh dari sistem optik yang menerima sinyal analog, seperti mata manusia, kamera analog

• Citra diskrit/digital : dihasilkan dari proses digitalisasi terhadap citra kontinyu

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Image Sampling

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Tahapan Sampling

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Sampling and Quantization

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sampled real image quantized sampled &

quantized


Sampling and Quantization

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sampled real image quantized sampled &

quantized

pixel grid column index

row

index

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Sampling

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),( crIS ,CI

continuous image sampled image

Take the average within each square.


Sampling

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),( crIS ,CI



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Sampling

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),( crIS ,CI




Sampling

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),( crIS ,CI



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Sampling dan Quantization

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Hasil Sampling dan Quantization

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Spatial Image Resolution: • Resolution

– Ukuran area citra yang direpresentasikan dengan piksel – Different Resolutions are possible (256x256….16x16)

• Lower resolution leads to data reduction!

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Digital Image

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a grid of squares,

each of which

contains a single

color

each square is

called a pixel (for

picture element)

Color images have 3 values per

pixel; monochrome images have 1

value per pixel.

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Pixels

• A digital image, I, is a mapping from a 2D grid of uniformly spaced discrete points, {p = (r,c)}, into a set of positive integer values, {I( p)}, or a set of vector values, e.g., {[R G B]T(p)}.

• At each column location in each row of I there is a value.

• The pair ( p, I( p) ) is called a “pixel” (for picture element).

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Pixels

• p = (r,c) is the pixel location indexed by row, r, and column, c.

• I( p) = I(r,c) is the value of the pixel at location p.

• If I( p) is a single number then I is monochrome.

• If I( p) is a vector (ordered list of numbers) then I has multiple bands (e.g., a color image).

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Pixels

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Pixel Location: p = (r , c)

Pixel Value: I(p) = I(r , c) Pixel : [ p, I(p)]


Pixels

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43

12

blue

green

red

)( pI

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277,272

col,row

,

##

crp

Pixel : [ p, I(p)]

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Tipe citra digital

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Citra Biner

Citra Keabuan

Citra Berwarna Citra Indeks


Ukuran Citra

• Jika diasumsikan sebuah citra biner berukuran 512 x 512, maka jumlah bit yang diperlukan untuk menyimpan citra ini adalah

• 512 x 512 x 1 bit = 262.144 = 32.768 bytes

= 32, 768 Kb = 0.033 Mb (asumsi 1 Kb = 1000 byte).

Bagaimana jika citra berwarna?

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Elemen Citra Digital

1. Kecerahan (Intensitas Cahaya) 2. Kontras : sebaran terang (lightness) dan gelap

(darkness) di dalam sebuah gambar 3. Kontur : keadaan yang ditimbulkan oleh

perubahan intensitas pada pixelpixel yang bertetangga

4. Warna: persepsi yang dirasakan oleh sistem visual manusia terhadap panjang gelombang cahaya yang dipantulkan oleh objek.

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kuliah 02 - pengolahan citra digital sampling quantization 2

Documents

pembentukan citra digital

menerima sinyal analog

1 departemen ilmu komputer

departemen ilmu komputer

12 departemen ilmu komputer

slide diambil

sistem optik

mata manusia