如何检查uiimage是否为空白? (空,透明) [英] How to check if a uiimage is blank? (empty, transparent)
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问题描述
这是检查 UIImage
是否为空白的最好方法?
我有这个绘画编辑器返回 UIImage
;
which is the best way to check whether a UIImage
is blank?
I have this painting editor which returns a UIImage
; I don't want to save this image if there's nothing on it.
推荐答案
Try this code:
BOOL isImageFlag=[self checkIfImage:image];
And checkIfImage method:
- (BOOL) checkIfImage:(UIImage *)someImage {
CGImageRef image = someImage.CGImage;
size_t width = CGImageGetWidth(image);
size_t height = CGImageGetHeight(image);
GLubyte * imageData = malloc(width * height * 4);
int bytesPerPixel = 4;
int bytesPerRow = bytesPerPixel * width;
int bitsPerComponent = 8;
CGContextRef imageContext =
CGBitmapContextCreate(
imageData, width, height, bitsPerComponent, bytesPerRow, CGImageGetColorSpace(image),
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big
);
CGContextSetBlendMode(imageContext, kCGBlendModeCopy);
CGContextDrawImage(imageContext, CGRectMake(0, 0, width, height), image);
CGContextRelease(imageContext);
int byteIndex = 0;
BOOL imageExist = NO;
for ( ; byteIndex < width*height*4; byteIndex += 4) {
CGFloat red = ((GLubyte *)imageData)[byteIndex]/255.0f;
CGFloat green = ((GLubyte *)imageData)[byteIndex + 1]/255.0f;
CGFloat blue = ((GLubyte *)imageData)[byteIndex + 2]/255.0f;
CGFloat alpha = ((GLubyte *)imageData)[byteIndex + 3]/255.0f;
if( red != 1 || green != 1 || blue != 1 || alpha != 1 ){
imageExist = YES;
break;
}
}
free(imageData);
return imageExist;
}
You will have to add OpenGLES framework and import this in the .m file:
#import <OpenGLES/ES1/gl.h>
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