Image Processing

Example of Digital image

Fine name: F_01.JPGType of file: JPEG ImageWidth: 512Height: 768Resolution: 96Bit Depth: 24Size: 46,744 bytes

Image Processing

Application Fields: Medicine

Image Processing

Application Fields: Geology

Image Processing

Application Fields: Image Enhancement

Image Processing

Application Fields: Entertainment

Image Processing

Image Processing

Image Processing

Image Processing

Image Processing

f(x,y) – color value of pixel at (x,y)

Digital image is set {f(x,y), for all pixels (x,y)}

or { f(x,y), 1≤x ≤W, 1≤y≤H }

x

y

Image Processing

Image Processing

Image Processing

Image Processing

Image Processing

Image Processing

Image Processing

Image Processing

Gray scale

The intensity of a monochrome image at any point (x,y) is called gray level of the image at the point (x,y) :

ℓ = f(x, y)

The range [Lmin, Lmax], where Lmin ℓ Lmax, is called

the gray scale.

Image Processing

Neighbors of a Pixel Let P is a pixel at coordinate (x, y).

Then, P has •two horizontal and •two vertical neighbors at

(x+1, y), (x-1, y), (x, y-1), (x, y+1) (1)

The set (1) is called The set (1) is called 4-neighbors of P.4-neighbors of P.

P(x,y)P(x,y)

Image Processing

Neighbors of a Pixel Let P is a pixel at coordinate (x, y). The 4 diagonal neighbors of P:

(x-1, y-1), (x-1, y+1), (x+1, y-1), (x+1, y+1) (2)

The set (1)&(2), The set (1)&(2), denoted by N8(P), is denoted by N8(P), is called 8-neighbors of P.called 8-neighbors of P.

P(x,y)

Image Processing

Color Model

Color Fundamentals

Image Processing

Color Model

Color Fundamentals

Image Processing

Color Model Total of 6-7.000.000 cones in the human eye.

They are divided into 3 principal sensing categories, corresponding to red, green, blue light.

Approximately, Approximately, 65% of all cones 65% of all cones are sensitive to are sensitive to RED lightRED light

Approximately, 33% Approximately, 33% are sensitive to are sensitive to GREEN lightGREEN light

And, approximately, 2% are And, approximately, 2% are sensitive to BLUE light (but the sensitive to BLUE light (but the blue cones are the most blue cones are the most sensitive)sensitive)

Image Processing

Color Model The International Commission on Illumination designated (1931) the following specific wavelength values to the three primary colors:

BLUE = 435.8 nm,BLUE = 435.8 nm,

GREEN = 546.1 nm, GREEN = 546.1 nm, RED = 700 nm RED = 700 nm

CIE standards CIE standards

Image Processing

Color Model

Image Processing

Color Model

Image Processing

Color Model

Mỗi mô hình màu gồm ba màu, ví dụ: {red, green, blue}, hoặc {cyan, magenta, yellow}

Ảnh xám:Mỗi điểm ảnh có các thành phần màu bằng nhau {red = a, green = a, blue= a},a – mức xám

Image Processing

Color Model

Image Processing

Pixels Let P(x, y) is some (discrete) point in the image, and f(P) is vector value of point P, eg.,

f(P) = [R(P), G(P), B(P)] if I is the color image and, f(P) is called intensity or gray level if I is dark-gray image (image have dark gray-level distributions)

The pair P & f(P)

is called a pixel (stand for picture element). Usually, used note f(x, y) to sign a pixel, where x, y are spatial coordinates.

Image Processing

Pixels Let P(x, y) is some (discrete) point in the image, and f(P) is vector value of point P, eg.,

f(P) = [R(P), G(P), B(P)] if I is the color image and, f(P) is called intensity or gray level if I is dark-gray image (image have dark gray-level distributions)

The pair P & f(P)

is called a pixel (stand for picture element). Usually, used note f(x, y) to sign a pixel, where x, y are spatial coordinates.

Một số phép toán xử lý ảnh

Nén dữ liệu ảnh

Size of Image file D.BMP is 65,322 bytes. Size of Image file D.JPG is 4,781 bytes.

Lọc nhiễu

Một số phép toán xử lý ảnh

Phân đoạn ảnh

Một số phép toán xử lý ảnh

Thủy ấn (Watermarking)

An image with visible An image with visible digital watermarking. The digital watermarking. The text text

""Brian Kell 2006Brian Kell 2006" " can be seen across the can be seen across the center of the image.center of the image.

Một số phép toán xử lý ảnh

Nhận dạng

Who?Who?

Một số phép toán xử lý ảnh

Origin image

Histogram equalization

-brightness-brightness +brightness+brightness

+contrast -contrast

=1.25=1.25 =0.9=0.9

negativenegativebit-plan 5bit-plan 5

Biến đổi điểm ảnh

Image Processing

How to practice and what is more reading? A typical BMP file usually contains the following blocks of data:

BMP File Header Stores general information BMP File Header Stores general information about the BMP file.about the BMP file.

Bitmap Information (DIB header)Stores detailed Bitmap Information (DIB header)Stores detailed information about the bitmap image.information about the bitmap image.

Color PaletteStores the definition of the colors Color PaletteStores the definition of the colors being used for indexed color bitmaps.being used for indexed color bitmaps.

Bitmap Data Stores the actual image, pixel by Bitmap Data Stores the actual image, pixel by pixel.pixel.

Image Processing

How to practice and what is more reading?

start size name stdvalue Purpose

1 2 bfType 19778 must always be set to 'BM' to declare that this is a .bmp-file.

3 4 bfSize ?? specifies the size of the file in bytes.

7 2 bfReserved1 0 must always be set to zero.

9 2 bfReserved2 0 must always be set to zero.

11 4 bfOffBits 1078 specifies the offset from the beginning of the file to the bitmap data.

Image Processingstart size name stdvalue Purpose

15 4 biSize 40 specifies the size of the BITMAPINFOHEADER structure, in bytes.

19 4 biWidth 100 specifies the width of the image, in pixels.

23 4 biHeight 100 specifies the height of the image, in pixels.

27 2 biPlanes 1 specifies the number of planes of the target device, must be set to zero.

29 2 biBitCount 8 specifies the number of bits per pixel.

31 4 biCompression 0 Specifies the type of compression, usually set to zero (no compression).

35 4 biSizeImage 0 specifies the size of the image data, in bytes. If there is no compression, it is valid to set this member to zero.

39 4 biXPelsPerMeter 0 specifies the the horizontal pixels per meter on the designated targer device, usually set to zero.

43 4 biYPelsPerMeter 0 specifies the the vertical pixels per meter on the designated targer device, usually set to zero.

47 4 biClrUsed 0

specifies the number of colors used in the bitmap, if set to zero the number of colors is calculated using the biBitCount member.

51 4 biClrImportant 0 specifies the number of color that are 'important' for the bitmap, if set to zero, all colors are important.

How to practice and what is more reading?How to practice and what is more reading?

Image Processing

Note:biBitCount actually specifies the color resolution of the bitmap. The possible values are:

1 (black/white);

4 (16 colors);

8 (256 colors);

24 (16.7 million colors).

The biBitCount data element also decides if there is a color table in the file and how it looks like:

In 1-bit mode the color table has to contain 2 entries (white, black).

In 4-bit mode the color table must contain 16 colors.

In 8-bit mode the color table contains 256 entries.

In 24-bit mode, the palette is omitted.

Image Processing

The color paletteThe color palette

start size name stdvalue purpose

1 1 rgbBlue - specifies the blue part of the color.

2 1 rgbGreen - specifies the green part of the color.

3 1 rgbRed - specifies the red part of the color.

4 1 rgbReserved - must always be set to zero.

Image Processing

Bitmap data:

It depens on the BMP File Header structure how the pixel data is to be interpreted.

Another important thing is that the number of bytes in one row must always be adjusted to fit into the border of a multiple of four.

Image Processing

Bitmap data:

In 1-bit mode every byte in the image data represents eight pixels. They are arranged from higher to lower bit for pixels from left to right.

In 4-bit mode every byte in the image data represents two pixels. The byte is split into the higher 4 bits and the lower 4 bits and each value of them points to a palette entry.

In 8-bit mode every byte represents a pixel. The value points to an entry in the color table.

In 24-bit mode, three bytes represent one pixel. The first byte represents the red part, the second the green and the third the blue part. No Color

Table

Image Processing

Ôn tập, tự học, thực hành:

1. Khái niệm ảnh số. Mô tả ảnh xám, ảnh màu.

2. Một số bài toán trong xử lý ảnh số.

3. Một số ứng dụng của xử lý ảnh số.

4. Các bước chính trong một hệ thống xử lý ảnh.

5. Sự hình thành ảnh trong mắt người. Quá trình thu nhận ảnh. Số hóa ảnh.

6. Mô hình màu RGB, HSI và công thức chuyển đổi giữa chúng.

7. Viết chương trình hiển thị ảnh, thay đổi màu của một số điểm ảnh.

8. Viết chương trình biến đổi từ ảnh màu (đa sắc) sang ảnh xám (và ngược lại?).

Image Processing

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