我一直在尝试使用 apache pdf box 在 pdf 中创建一个三角形。 使用 PDShadingType4 类。下面是代码实现，但它只创建了空的 pdf。我在apache提供的示例中没有发现任何PDShadingType4的实现。
生成的三角形应该类似于 pdf 左下角的三角形 link可以在 apache pdf 框 issue 中找到
我找不到任何使用 PDShadingType4 的着色示例。</p>
下面的实现正确吗？或者他们是使用 PDShadingType4 实现着色(三角形)的其他方式
import java.io.IOException;
import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSFloat;
import org.apache.pdfbox.cos.COSInteger;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.cos.COSStream;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.common.function.PDFunctionType2;
import org.apache.pdfbox.pdmodel.graphics.color.PDDeviceRGB;
import org.apache.pdfbox.pdmodel.graphics.shading.PDShading;
import org.apache.pdfbox.pdmodel.graphics.shading.PDShadingType4;
public class TriangleGraident2 {
public void create(String file) throws IOException {
PDDocument document = null;
try {
document = new PDDocument();
PDPage page = new PDPage();
document.addPage(page);
PDPageContentStream contentStream = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, false);
contentStream.moveTo(38, 17);
COSStream fdict = new COSStream();
fdict.setInt(COSName.FUNCTION_TYPE, 2);
COSArray cosArray = new COSArray();
cosArray.add(COSInteger.get(104));
cosArray.add(COSInteger.get(83));
cosArray.add(COSInteger.get(170));
cosArray.add(COSInteger.get(17));
cosArray.add(COSInteger.get(38));
cosArray.add(COSInteger.get(17));
/*Setting color */
COSArray c0 = new COSArray();
c0.add(COSFloat.get("1"));
c0.add(COSFloat.get("0"));
c0.add(COSFloat.get("0"));
COSArray c1 = new COSArray();
c1.add(COSFloat.get("0.5"));
c1.add(COSFloat.get("1"));
c1.add(COSFloat.get("0.5"));
/*Setting color*/
COSArray decode = new COSArray();
decode.add(COSFloat.get("0.0"));
decode.add(COSFloat.get("1.0"));
decode.add(COSFloat.get("0.0"));
decode.add(COSFloat.get("1.0"));
decode.add(COSFloat.get("0.0"));
fdict.setItem(COSName.C0, c0);
fdict.setItem(COSName.C1, c1);
PDFunctionType2 func = new PDFunctionType2(fdict);
PDShadingType4 shading = new PDShadingType4(fdict);
shading.setColorSpace(PDDeviceRGB.INSTANCE);
shading.setShadingType(PDShading.SHADING_TYPE4);
shading.getCOSObject().setInt(COSName.LENGTH, 32);
shading.setBitsPerCoordinate(24);
shading.setBitsPerComponent(16);
shading.setBitsPerFlag(8);
shading.getCOSObject().setItem(COSName.COORDS, cosArray);
shading.setDecodeValues(decode);
shading.setFunction(func);
contentStream.shadingFill(shading);
contentStream.close();
document.save(file);
document.close();
}
finally {
if (document != null) {
document.close();
}
}
}
public static void main(String[] args) throws IOException {
TriangleGraident2 creator = new TriangleGraident2();
creator.create("C:\\Users\\abc\\Desktop\\triangle_image.pdf");
}
}
最佳答案
此代码在左下角创建一个 Gouraud 阴影三角形:
// See PDF 32000 specification,
// 8.7.4.5.5 Type 4 Shadings (Free-Form Gouraud-Shaded Triangle Meshes)
PDShadingType4 gouraudShading = new PDShadingType4(new COSStream());
gouraudShading.setShadingType(PDShading.SHADING_TYPE4);
// we use multiple of 8, so that no padding is needed
gouraudShading.setBitsPerFlag(8);
gouraudShading.setBitsPerCoordinate(16);
gouraudShading.setBitsPerComponent(8);
COSArray decodeArray = new COSArray();
// coordinates x y map 16 bits 0..FFFF to 0..FFFF to make your life easy
// so no calculation is needed, but you can only use integer coordinates
// for real numbers, you'll need smaller bounds, e.g. 0xFFFF / 0xA = 0x1999
// would allow 1 point decimal result coordinate.
// See in PDF specification: 8.9.5.2 Decode Arrays
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.get(0xFFFF));
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.get(0xFFFF));
// colors r g b map 8 bits from 0..FF to 0..1
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
gouraudShading.setDecodeValues(decodeArray);
gouraudShading.setColorSpace(PDDeviceRGB.INSTANCE);
// Function is not required for type 4 shadings and not really useful,
// because if a function would be used, each edge "color" of a triangle would be one value,
// which would then transformed into n color components by the function so it is
// difficult to get 3 "extremes".
OutputStream os = ((COSStream) gouraudShading.getCOSObject()).createOutputStream();
MemoryCacheImageOutputStream mcos = new MemoryCacheImageOutputStream(os);
// Vertex 1, starts with flag1
// (flags always 0 for vertices of start triangle)
mcos.writeByte(0);
// x1 y1 (left corner)
mcos.writeShort(0);
mcos.writeShort(0);
// r1 g1 b1 (red)
mcos.writeByte(0xFF);
mcos.writeByte(0);
mcos.writeByte(0);
// Vertex 2, starts with flag2
mcos.writeByte(0);
// x2 y2 (top corner)
mcos.writeShort(100);
mcos.writeShort(100);
// r2 g2 b2 (green)
mcos.writeByte(0);
mcos.writeByte(0xFF);
mcos.writeByte(0);
// Vertex 3, starts with flag3
mcos.writeByte(0);
// x3 y3 (right corner)
mcos.writeShort(200);
mcos.writeShort(0);
// r3 g3 b3 (blue)
mcos.writeByte(0);
mcos.writeByte(0);
mcos.writeByte(0xFF);
mcos.close();
// outside stream MUST be closed as well, see javadoc of MemoryCacheImageOutputStream
os.close();
要运行着色，请调用
contentStream.shadingFill(gouraudShading);
这是一个不同的解码数组，与您链接到的示例 PDF 中的数组类似，尽管我只使用了 16 位而不是 24 位:
COSArray decodeArray = new COSArray();
// coordinates x y map 16 bits 0..FFFF to -16384..16384
// this means that 0x8000 maps to 0
// some other useful values
// - 0x862C maps to top of A4 page
// - 0x84C4 maps to right of A4 page
// - 0x8262 maps to horizontal middle of A4 page
decodeArray.add(COSInteger.get(-16384));
decodeArray.add(COSInteger.get(16384));
decodeArray.add(COSInteger.get(-16384));
decodeArray.add(COSInteger.get(16384));
// colors r g b map 8 bits from 0..FF to 0..1
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
decodeArray.add(COSInteger.ZERO);
decodeArray.add(COSInteger.ONE);
gouraudShading.setDecodeValues(decodeArray);
三角形的坐标将为 0x8000 0x8000、0x8100 0x8100、0x8200 0x8000。
关于java - 使用 PDShadingType4 Apache pdf box 实现类型 4 阴影，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43768398/