63 lines
2.8 KiB
Go
63 lines
2.8 KiB
Go
package sign
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import (
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"bytes"
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"fmt"
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)
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func (context *SignContext) createAppearance(rect [4]float64) ([]byte, error) {
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text := context.SignData.Signature.Info.Name
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rectWidth := rect[2] - rect[0]
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rectHeight := rect[3] - rect[1]
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if rectWidth < 1 || rectHeight < 1 {
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return nil, fmt.Errorf("invalid rectangle dimensions: width %.2f and height %.2f must be greater than 0", rectWidth, rectHeight)
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}
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// Calculate font size
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fontSize := rectHeight * 0.8 // Initial font size
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textWidth := float64(len(text)) * fontSize * 0.5 // Approximate text width
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if textWidth > rectWidth {
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fontSize = rectWidth / (float64(len(text)) * 0.5) // Adjust font size to fit text within rect width
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}
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var appearance_stream_buffer bytes.Buffer
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appearance_stream_buffer.WriteString("q\n") // Save graphics state
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appearance_stream_buffer.WriteString("BT\n") // Begin text
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appearance_stream_buffer.WriteString(fmt.Sprintf("/F1 %.2f Tf\n", fontSize)) // Font and size
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appearance_stream_buffer.WriteString(fmt.Sprintf("0 %.2f Td\n", rectHeight-fontSize)) // Position in unit square
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appearance_stream_buffer.WriteString("0.2 0.2 0.6 rg\n") // Set font color to ballpoint-like color (RGB)
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appearance_stream_buffer.WriteString(fmt.Sprintf("%s Tj\n", pdfString(text))) // Show text
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appearance_stream_buffer.WriteString("ET\n") // End text
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appearance_stream_buffer.WriteString("Q\n") // Restore graphics state
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var appearance_buffer bytes.Buffer
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appearance_buffer.WriteString("<<\n")
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appearance_buffer.WriteString(" /Type /XObject\n")
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appearance_buffer.WriteString(" /Subtype /Form\n")
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appearance_buffer.WriteString(fmt.Sprintf(" /BBox [0 0 %f %f]\n", rectWidth, rectHeight))
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appearance_buffer.WriteString(" /Matrix [1 0 0 1 0 0]\n") // No scaling or translation
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// Resources dictionary
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appearance_buffer.WriteString(" /Resources <<\n")
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appearance_buffer.WriteString(" /Font <<\n")
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appearance_buffer.WriteString(" /F1 <<\n")
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appearance_buffer.WriteString(" /Type /Font\n")
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appearance_buffer.WriteString(" /Subtype /Type1\n")
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appearance_buffer.WriteString(" /BaseFont /Times-Roman\n")
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appearance_buffer.WriteString(" >>\n")
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appearance_buffer.WriteString(" >>\n")
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appearance_buffer.WriteString(" >>\n")
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appearance_buffer.WriteString(" /FormType 1\n")
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appearance_buffer.WriteString(fmt.Sprintf(" /Length %d\n", appearance_stream_buffer.Len()))
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appearance_buffer.WriteString(">>\n")
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appearance_buffer.WriteString("stream\n")
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appearance_buffer.Write(appearance_stream_buffer.Bytes())
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appearance_buffer.WriteString("endstream\n")
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return appearance_buffer.Bytes(), nil
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}
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