我正在尝试使用pydicom创建一个JPEG压缩的DICOM图像。有一份关于彩色DICOM图像的好资料可以在这里找到,但它主要是理论和C++。在下面的代码示例中,我在
output-raw.dcm
(未压缩)中创建了一个苍白的蓝色椭圆形,看起来很好:
import io
from PIL import Image, ImageDraw
from pydicom.dataset import Dataset
from pydicom.uid import generate_uid, JPEGExtended
from pydicom._storage_sopclass_uids import SecondaryCaptureImageStorage
WIDTH = 100
HEIGHT = 100
def ensure_even(stream):
# Very important for some viewers
if len(stream) % 2:
return stream + b"\x00"
return stream
def bob_ross_magic():
image = Image.new("RGB", (WIDTH, HEIGHT), color="red")
draw = ImageDraw.Draw(image)
draw.rectangle([10, 10, 90, 90], fill="black")
draw.ellipse([30, 20, 70, 80], fill="cyan")
draw.text((11, 11), "Hello", fill=(255, 255, 0))
return image
ds = Dataset()
ds.is_little_endian = True
ds.is_implicit_VR = True
ds.SOPClassUID = SecondaryCaptureImageStorage
ds.SOPInstanceUID = generate_uid()
ds.fix_meta_info()
ds.Modality = "OT"
ds.SamplesPerPixel = 3
ds.BitsAllocated = 8
ds.BitsStored = 8
ds.HighBit = 7
ds.PixelRepresentation = 0
ds.PhotometricInterpretation = "RGB"
ds.Rows = HEIGHT
ds.Columns = WIDTH
image = bob_ross_magic()
ds.PixelData = ensure_even(image.tobytes())
image.save("output.png")
ds.save_as("output-raw.dcm", write_like_original=False) # File is OK
#
# Create compressed image
#
output = io.BytesIO()
image.save(output, format="JPEG")
ds.PixelData = ensure_even(output.getvalue())
ds.PhotometricInterpretation = "YBR_FULL_422"
ds.file_meta.TransferSyntaxUID = JPEGExtended
ds.save_as("output-jpeg.dcm", write_like_original=False) # File is corrupt
最后,我试图创建压缩的DICOM文件:我尝试使用不同的传输语法、使用PIL进行压缩,但都没有成功。我认为生成的DICOM文件是损坏的。如果我将原始的DICOM文件转换为使用gdcm-tools进行JPEG压缩:
$ gdcmconv -J output-raw.dcm output-jpeg.dcm
通过在这个转换后的文件上执行dcmdump
命令,我们可以看到一个有趣的结构,但我不知道如何使用pydicom来复制它:
$ dcmdump output-jpeg.dcm
# Dicom-File-Format
# Dicom-Meta-Information-Header
# Used TransferSyntax: Little Endian Explicit
(0002,0000) UL 240 # 4, 1 FileMetaInformationGroupLength
(0002,0001) OB 00\01 # 2, 1 FileMetaInformationVersion
(0002,0002) UI =SecondaryCaptureImageStorage # 26, 1 MediaStorageSOPClassUID
(0002,0003) UI [1.2.826.0.1.3680043.8.498.57577581978474188964358168197934098358] # 64, 1 MediaStorageSOPInstanceUID
(0002,0010) UI =JPEGLossless:Non-hierarchical-1stOrderPrediction # 22, 1 TransferSyntaxUID
(0002,0012) UI [1.2.826.0.1.3680043.2.1143.107.104.103.115.2.8.4] # 48, 1 ImplementationClassUID
(0002,0013) SH [GDCM 2.8.4] # 10, 1 ImplementationVersionName
(0002,0016) AE [gdcmconv] # 8, 1 SourceApplicationEntityTitle
# Dicom-Data-Set
# Used TransferSyntax: JPEG Lossless, Non-hierarchical, 1st Order Prediction
...
... ### How to do the magic below?
...
(7fe0,0010) OB (PixelSequence #=2) # u/l, 1 PixelData
(fffe,e000) pi (no value available) # 0, 1 Item
(fffe,e000) pi ff\d8\ff\ee\00\0e\41\64\6f\62\65\00\64\00\00\00\00\00\ff\c3\00\11... # 4492, 1 Item
(fffe,e0dd) na (SequenceDelimitationItem) # 0, 0 SequenceDelimitationItem
我尝试使用pydicom的encaps模块, 但我认为它主要用于读取数据,而不是写入。还有其他人有什么想法来处理这个问题吗?如何创建/编码这些PixelSequence
?希望能在纯Python中创建JPEG压缩的DICOM文件,而不运行外部工具。