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[英]OSX - Loading an image and saving it as a smaller png file using Swift
[英]Wrong rotation when loading image using CGImageSourceRef
我使用下面的代碼在C ++庫中加載圖像。 加載某些圖像時,圖像的旋轉是錯誤的。 它似乎會影響來自iPhone相機的JPEG。 我該如何解決?
據推測,有一個標志位於相機捕獲的JPEG設置。 以這種方式加載圖像時我不確定如何訪問它。
CGImageSourceRef source = CGImageSourceCreateWithURL(url, NULL);
CFRelease(url);
if(source==NULL)
return IM_ErrFileError;
CGImageRef image = CGImageSourceCreateImageAtIndex(source, 0, NULL);
CFRelease(source);
if(image==NULL)
return IM_ErrFileError;
int w = (int)CGImageGetWidth(image);
int h = (int)CGImageGetHeight(image);
im::Err err = img.Create(im::IntSize(w, h), bands, sizeof(uint8_t), imgtype);
if(IM_FAILED(err))
{
CGImageRelease(image);
return err;
}
img.Clear();
CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(colorspacename);
if(colorSpace==NULL)
{
CGImageRelease(image);
return IM_ErrAlloc;
}
// Create RGBA context
CGContextRef context = CGBitmapContextCreate(img.BytePtr(), w, h, 8, img.StrideBytes(), colorSpace, alphainfo);
if(context==NULL)
{
CGColorSpaceRelease(colorSpace);
CGImageRelease(image);
return IM_ErrAlloc;
}
CGColorSpaceRelease(colorSpace);
CGRect rect;
rect.origin.x = 0;
rect.origin.y = 0;
rect.size.width = w;
rect.size.height = h;
CGContextDrawImage(context, rect, image);
CGContextRelease(context);
CGImageRelease(image);
基於答案,這是我修改代碼的方式。 首先得到方向:
int orientation = 1;
CFDictionaryRef dict = CGImageSourceCopyPropertiesAtIndex(source, 0, NULL);
if(dict)
{
CFNumberRef imageOrientation;
if(CFDictionaryGetValueIfPresent(dict, kCGImagePropertyOrientation, (const void **)&imageOrientation))
{
if(imageOrientation)
CFNumberGetValue(imageOrientation, kCFNumberIntType, &orientation);
}
CFRelease(dict);
}
確保尺寸正確:
int width = (int)CGImageGetWidth(image);
int height = (int)CGImageGetHeight(image);
int canvasw, canvash;
if(orientation<=4)
{
canvasw = width;
canvash = height;
}
else
{
canvasw = height;
canvash = width;
}
使用畫布大小創建位圖上下文圖像。 渲染時補償方向:
switch(orientation)
{
case 2:
// 2 = 0th row is at the top, and 0th column is on the right - Flip Horizontal
CGContextConcatCTM(context, CGAffineTransformMake(-1.0, 0.0, 0.0, 1.0, width, 0.0));
break;
case 3:
// 3 = 0th row is at the bottom, and 0th column is on the right - Rotate 180 degrees
CGContextConcatCTM(context, CGAffineTransformMake(-1.0, 0.0, 0.0, -1.0, width, height));
break;
case 4:
// 4 = 0th row is at the bottom, and 0th column is on the left - Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(1.0, 0.0, 0, -1.0, 0.0, height));
break;
case 5:
// 5 = 0th row is on the left, and 0th column is the top - Rotate -90 degrees and Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(0.0, -1.0, -1.0, 0.0, height, width));
break;
case 6:
// 6 = 0th row is on the right, and 0th column is the top - Rotate 90 degrees
CGContextConcatCTM(context, CGAffineTransformMake(0.0, -1.0, 1.0, 0.0, 0.0, width));
break;
case 7:
// 7 = 0th row is on the right, and 0th column is the bottom - Rotate 90 degrees and Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(0.0, 1.0, 1.0, 0.0, 0.0, 0.0));
break;
case 8:
// 8 = 0th row is on the left, and 0th column is the bottom - Rotate -90 degrees
CGContextConcatCTM(context, CGAffineTransformMake(0.0, 1.0, -1.0, 0.0, height, 0.0));
break;
default:
break;
}
我實際上沒有嘗試使用iPhone圖像,但我建議使用CGImageSourceCopyPropertiesAtIndex
來獲取kCGImagePropertyOrientation
。 一旦知道了正確的方向,就可以在繪制時應用一些變換。
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