A method for intelligently stamping PDF files

Abstract

A method for intelligently stamping a PDF file, comprising the following steps: step 1, traversing all pages of the PDF file to obtain data defining the page; step 2, generating a cache image at a predetermined resolution; step 3, counting the proportion of white pixels for the cache image; step 4, establishing a proportional relationship between the pixels of the stamp to be stamped and the unit pixel points of the PDF file, and selecting the stamping position according to the proportional relationship.

Description

Technical Field

[0001] This invention relates to the field of electronic seals, and in particular to a method for intelligently stamping PDF files. Background Technology

[0002] This image-analysis-based intelligent PDF stamping system aims to address the pain points of traditional electronic signatures, such as fixed placement and inability to adapt to dynamic pages. Utilizing Java and Apache PDFBox, it implements four core functions: PDF parsing, page rendering, image analysis, and coordinate mapping. It dynamically converts PDF pages into images, intelligently locating the position with the highest blank area (threshold ≥80%) in candidate areas such as the corners and center, and accurately overlaying the stamp. The system supports multiple page sizes and complex document layouts, achieving a single-page processing efficiency of less than 500ms. It can be applied to scenarios such as electronic contracts and automated office work, significantly improving document processing efficiency and intelligence. Summary of the Invention

[0003] Therefore, this invention proposes a method for intelligently stamping PDF files, comprising the following steps: Step 1: Traverse all pages of the PDF file to obtain the data that defines the page; Step 2: Generate a cached image at a predetermined resolution; Step 3: Calculate the percentage of white pixels in the cached image; Step 4: Establish the ratio between the pixels of the stamp to be stamped and the unit pixels of the PDF file, and select the position to stamp accordingly.

[0004] Preferably, the data defining the page includes size and orientation.

[0005] Preferably, step 3-1 is further included between step 3 and step 4, which calculates the size of the stamp pixels by predefining a fixed stamp size and the resolution.

[0006] Preferably, the PDF file includes electronic contracts, policy documents, and explanatory documents.

[0007] Preferably, the resolution is greater than or equal to 150 DPI.

[0008] Preferably, the white pixel has an RGB value of >= 240.

[0009] Preferably, step 3 includes predefining the four corners and center candidate areas of the cached image.

[0010] Preferably, the position with the highest blank rate is intelligently located in the four corners and the center candidate areas.

[0011] Preferably, the blank rate is >= 80%.

[0012] Preferably, after finding a suitable location from the candidate region, the pixel coordinates of the corresponding region are mapped to PDF point coordinates and filled onto the PDF file.

[0013] This specifically involved requirements analysis and technology selection, clarifying the need for dynamic stamping, comparing tools such as iText and PDFBox, and selecting Apache PDFBox as the core library. The technical approach was determined to be "rendering-analysis-positioning," prioritizing the resolution of coordinate transformation and blank space detection issues. In the core module development, PDF parsing was performed: traversing the PDF page to obtain metadata such as size and orientation. Image rendering: using PDFRenderer to generate a BufferedImage at 150 DPI, balancing clarity and performance. Blank space analysis: predefining candidate areas for the four corners and center, and statistically analyzing the proportion of white pixels (RGB≥240). Coordinate mapping: establishing the proportional relationship between image pixels and PDF point units to ensure accurate stamp positioning. Key technical breakthroughs included: Dynamic adaptation: calculating the stamp pixel size based on page size and DPI, compatible with different page widths and heights. Performance optimization: limiting the number of candidate areas to avoid performance bottlenecks caused by full-image scanning. Error control: introducing coordinate offset compensation to solve the problem of differences in the PDF coordinate system origin.

[0014] During the development of this invention, defect verification and improvements were carried out. Tests revealed a problem with misjudging dark backgrounds, and a temporary solution was to increase the blank rate threshold to 80%. Regarding the memory usage of large files, the approach was optimized to process them page by page instead of loading them entirely into memory. Attached Figure Description

[0015] Figure 1 The diagram shows the effect of using the present invention. Detailed Implementation

[0016] A method for intelligently stamping PDF files includes the following steps: Step 1: Traverse all pages of the PDF file to obtain the data that defines the page; Step 2: Generate a cached image at a predetermined resolution; Step 3: Calculate the percentage of white pixels in the cached image; Step 4: Establish the ratio between the pixels of the stamp to be stamped and the unit pixels of the PDF file, and select the position to stamp accordingly.

[0017] Preferably, the data defining the page includes size and orientation.

[0018] Preferably, step 3-1 is further included between step 3 and step 4, which calculates the size of the stamp pixels by predefining a fixed stamp size and the resolution.

[0019] Preferably, the PDF file includes electronic contracts, policy documents, and explanatory documents.

[0020] Preferably, the resolution is greater than or equal to 150 DPI.

[0021] Preferably, the white pixel has an RGB value of >= 240.

[0022] Preferably, step 3 includes predefining the four corners and center candidate areas of the cached image.

[0023] Preferably, the position with the highest blank rate is intelligently located in the four corners and the center candidate areas.

[0024] Preferably, the blank rate is >= 80%.

[0025] Preferably, after finding a suitable location from the candidate region, the pixel coordinates of the corresponding region are mapped to PDF point coordinates and filled onto the PDF file.

[0026] This specifically involved requirements analysis and technology selection, clarifying the need for dynamic stamping, comparing tools such as iText and PDFBox, and selecting Apache PDFBox as the core library. The technical approach was determined to be "rendering-analysis-positioning," prioritizing the resolution of coordinate transformation and blank space detection issues. In the core module development, PDF parsing was performed: traversing the PDF page to obtain metadata such as size and orientation. Image rendering: using PDFRenderer to generate a BufferedImage at 150 DPI, balancing clarity and performance. Blank space analysis: predefining candidate areas for the four corners and center, and statistically analyzing the proportion of white pixels (RGB≥240). Coordinate mapping: establishing the proportional relationship between image pixels and PDF point units to ensure accurate stamp positioning. Key technical breakthroughs included: Dynamic adaptation: calculating the stamp pixel size based on page size and DPI, compatible with different page widths and heights. Performance optimization: limiting the number of candidate areas to avoid performance bottlenecks caused by full-image scanning. Error control: introducing coordinate offset compensation to solve the problem of differences in the PDF coordinate system origin.

[0027] During the development of this invention, defect verification and improvements were carried out. Tests revealed a problem with misjudging dark backgrounds, and a temporary solution was to increase the blank rate threshold to 80%. Regarding the memory usage of large files, the approach was optimized to process them page by page instead of loading them entirely into memory.

[0028] like Figure 1 As shown, this invention can efficiently and effectively generate stamped PDF files, reducing workload while improving accuracy and satisfaction.

[0029] Preferred embodiments of the present invention have been exemplified above with reference to the accompanying drawings. However, those skilled in the art should understand that, without departing from the scope of protection of the appended claims, they can form new technical solutions by adding features, combining features, etc.

Claims

1. A method for intelligently stamping PDF files, characterized in that, Includes the following steps: Step 1: Traverse all pages of the PDF file to obtain the data that defines the page; Step 2: Generate a cached image at a predetermined resolution; Step 3: Calculate the percentage of white pixels in the cached image; Step 4: Establish the ratio between the pixels of the stamp to be stamped and the unit pixels of the PDF file, and select the position to stamp accordingly.

2. The method for intelligently stamping PDF files according to claim 1, characterized in that, The data defining this page includes its size and orientation.

3. The method for intelligently stamping PDF files according to claim 2, characterized in that, The step between step 3 and step 4 includes step 3-1, which calculates the size of the stamp pixels by using a predefined fixed stamp size and the resolution.

4. The method for intelligently stamping PDF files according to claim 3, characterized in that, The PDF files include electronic contracts, policy documents, and explanatory documents.

5. The method for intelligently stamping PDF files according to claim 4, characterized in that, The resolution is greater than or equal to 150 DPI.

6. The method for intelligently stamping PDF files according to claim 5, characterized in that, The white pixel has an RGB value greater than or equal to 240.

7. The method for intelligently stamping PDF files according to claim 6, characterized in that, Step 3 includes predefining the four corners and center candidate areas of the cached image.

8. The method for intelligently stamping PDF files according to claim 7, characterized in that, The system intelligently locates the position with the highest blank rate in the four corner and center candidate areas.

9. The method for intelligently stamping PDF files according to claim 8, characterized in that, The blank rate is >= 80%.

10. The method for intelligently stamping PDF files according to claim 9, characterized in that, After finding a suitable location from the candidate region, the pixel coordinates of the corresponding region are mapped to PDF point coordinates and then filled onto the PDF file.

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