def image_to_data(img,
compression_quality=95,
fmt='JPEG',
png_compression_level=9,
jpeg_optimized=True,
jpeg_progressive=False):
'''
Serialize image to bytestring in the specified format.
:param compression_quality: is for JPEG and goes from 0 to 100. 100 being lowest compression, highest image quality
:param png_compression_level: is for PNG and goes from 0-9. 9 being highest compression.
:param jpeg_optimized: Turns on the 'optimize' option for libjpeg which losslessly reduce file size
:param jpeg_progressive: Turns on the 'progressive scan' option for libjpeg which allows JPEG images to be downloaded in streaming fashion
'''
fmt = fmt.upper()
ba = QByteArray()
buf = QBuffer(ba)
buf.open(QBuffer.WriteOnly)
if fmt == 'GIF':
w = QImageWriter(buf, b'PNG')
w.setQuality(90)
if not w.write(img):
raise ValueError('Failed to export image as ' + fmt +
' with error: ' + w.errorString())
from PIL import Image
im = Image.open(BytesIO(ba.data()))
buf = BytesIO()
im.save(buf, 'gif')
return buf.getvalue()
is_jpeg = fmt in ('JPG', 'JPEG')
w = QImageWriter(buf, fmt.encode('ascii'))
if is_jpeg:
if img.hasAlphaChannel():
img = blend_image(img)
# QImageWriter only gained the following options in Qt 5.5
if jpeg_optimized and hasattr(QImageWriter, 'setOptimizedWrite'):
w.setOptimizedWrite(True)
if jpeg_progressive and hasattr(QImageWriter,
'setProgressiveScanWrite'):
w.setProgressiveScanWrite(True)
w.setQuality(compression_quality)
elif fmt == 'PNG':
cl = min(9, max(0, png_compression_level))
w.setQuality(10 * (9 - cl))
if not w.write(img):
raise ValueError('Failed to export image as ' + fmt + ' with error: ' +
w.errorString())
return ba.data()
def rotateR(self):
# Load image for QImageWriter
self.myImg = QImageWriter('testImage.png')
# Rotate image with QImageWriter transformation function
self.myImg.setTransformation(QImageIOHandler.TransformationRotate90)
self.updateImage()
