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Optimized Image Compression Method for PNG Format Disclosure Number: IPCOM000247641D
Publication Date: 2016-Sep-22
Document File: 3 page(s) / 61K

Publishing Venue

The Prior Art Database


Images with PNG(Portable Network Graphic) format require less storage space, compared with BMP(Bit-Map) format. The file size will be reduced when a BMP image file is transformed to a PNG format. This invention proposes one way to improve the compression ratio of transformation from BMP to PNG. This invention provides an optimized way to improve the compression ratio of transformation from BMP to PNG. It will help to make the PNG file less than traditional PNG compression, and require less storage space. This optimized compression method is data lossless method. The quality the image will not be impact compared with the traditional PNG format. Experiment shows the compression ratio can be improved significantly than the traditional PNG format file.

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Optimized Image Compression Method for PNG Format

The core idea of the invention is to transform the BMP image file to a temporary file, rearrange the pixels of the temporary file and then save the file as PNG format. The rearrange rule of the temporary file is as below
a. Create a temporary file, get the original BMP image file size (W, H), where W/H is the width/height of the image.

b. Divide image into blocks, the size the block is defined by users, here is (m, n). The total number of the blocks K can be calculated as below:

c. Fetch the first pixel from each blocks, save the pixel into the temporary file. Then the fetch the second pixel, and so on.

d. Finally one new file is generated with the same size as the image file. This file can be saved as a PNG format file.

e. When transform the PNG file back to the original BMP file, reading the image, it will do the reverse process transform as above steps.

Below shows an example of the process:
a. Test image size is 512*512, as shown in Fig.1

Fig.1 Test Image

b. Define the size of block is 4*4. Divide the test image into blocks.

c. Re-write pixel of block to image, as shown in Fig.2


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Fig.2 New Image after re-write

Fig.3 Recovery Image

Table.1 Result of Gray Images

d. Store the new image file as PNG file
e. When transform back, do the reverse process and recovery the original image file, as shown in Fig.3

Experiment Results:

In the experiment, 190 gray images and 10 color images (RGB) with BMP format ar...