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2024-10-14 13:10:57 +05:30
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@@ -146,12 +146,12 @@ Since PDF files almost always contain binary data, they can become corrupted if
- For example: %âãÏÓ - For example: %âãÏÓ
- The percent sign indicates another header line, the other few bytes are arbitrary character codes in excess of 127. So, the whole header in our example is: - The percent sign indicates another header line, the other few bytes are arbitrary character codes in excess of 127. So, the whole header in our example is:
%PDF-1.0 %PDF-1.0
%âãÏÓ %âãÏÓ
### Body ### Body
- The file body consists of a sequence of objects, each preceded by an object number, generation number, and the obj keyword on one line, and followed by the endobj keyword on another. The file body consists of a sequence of objects, each preceded by an object number, generation number, and the obj keyword on one line, and followed by the endobj keyword on another.
- For Example - For Example:
''' '''
1 0 obj 1 0 obj
<< <<
@@ -164,11 +164,11 @@ endobj
- Here, the object number is 1, and the generation number is 0 (it almost always is). The content for object 1 is in between the two lines 1 0 obj and endobj. In this case, it’s the dictionary <</Kids [2 0 R] /Count 1 /Type /Pages>> - Here, the object number is 1, and the generation number is 0 (it almost always is). The content for object 1 is in between the two lines 1 0 obj and endobj. In this case, it’s the dictionary <</Kids [2 0 R] /Count 1 /Type /Pages>>
### Cross-Reference Table ### Cross-Reference Table
- The cross-reference table lists the byte offset of each object in the file body. The cross-reference table lists the byte offset of each object in the file body.
- This allows random access to objects, meaning they don't have to be read in order. This allows random access to objects, meaning they don't have to be read in order.
- Objects that are not used are never read, making the process efficient. Objects that are not used are never read, making the process efficient.
- Operations like counting the number of pages in a PDF document are fast, even in large files. Operations like counting the number of pages in a PDF document are fast, even in large files.
- Each object has an object number and a generation number. Each object has an object number and a generation number.
- Generation numbers are used when a cross-reference table entry is reused. - Generation numbers are used when a cross-reference table entry is reused.
- For simplicity, we would assume generation numbers to be always zero and ignore them. - For simplicity, we would assume generation numbers to be always zero and ignore them.
- The cross-reference table consists of: - The cross-reference table consists of: