多削波Rects到核芯显卡创建拼贴

Question

我创建一个拼贴与来自其它图像元素结合。下面是一些ASCII艺术来解释我在做什么：

Given images A, B and C,
AAA, BBB, CCC
AAA, BBB, CCC
AAA, BBB, CCC

I take part of A, part of B and part of C as columns:

Axx, xBx, xxC
Axx, xBx, xxC
Axx, xBx, xxC

...and combine them in one image like this:

ABC
ABC
ABC

where the first 1/3rd of the image is a colum of A's pic, the middle is a column of B's pic and the last is a column of C's pic.

我有一些代码编写的，但它只是显示第一列，而不是休息......我觉得我必须以某种方式清除剪裁，BT我不知道怎么做，或是否这甚至是最好的办法。

+ (UIImage *)collageWithSize:(NSInteger)size fromImages:(NSArray *)images {
    NSMutableArray *selectedImages = [NSMutableArray array];
    [selectedImages addObjectsFromArray:images];

    // use the selectedImages for generating the thumbnail
    float columnWidth = (float)size/(float)[selectedImages count];

    //create a context to do our clipping in
    UIGraphicsBeginImageContext(CGSizeMake(size, size));
    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    for (int i = 0; i < [selectedImages count]; i++) {
        // get the current image
        UIImage *image = [selectedImages objectAtIndex:i];

        //create a rect with the size we want to crop the image to
        CGRect clippedRect = CGRectMake(i*columnWidth, 0, columnWidth, size);
        CGContextClipToRect(currentContext, clippedRect);

        //create a rect equivalent to the full size of the image
        CGRect drawRect = CGRectMake(0, 0, size, size);

        //draw the image to our clipped context using our offset rect
        CGContextDrawImage(currentContext, drawRect, image.CGImage);
    }

    //pull the image from our cropped context
    UIImage *collage = UIGraphicsGetImageFromCurrentImageContext();

    //pop the context to get back to the default
    UIGraphicsEndImageContext();

    //Note: this is autoreleased
    return collage;
}

我在做什么错了？

PS图像被绘制上下颠倒了。

Answer 1

CGContextClipToRect相交与设置参数的当前剪辑矩形。所以，你把它叫做第二次时，实际上是把你的裁剪区域不了了之。

有没有办法恢复剪切区域而不恢复图形状态。所以，拨打电话，在你的循环顶部和呼叫在底部CGContextSaveGState到CGContextRestoreGState。

在倒置部分可通过调节电流的变换矩阵是固定的：调用CGContextTranslateCTM移动原点，然后CGContextScaleCTM翻转y轴

Answer 2

在上下颠倒的图像可以通过调用以下方法进行修正：

CGImageRef flip (CGImageRef im) {
CGSize sz = CGSizeMake(CGImageGetWidth(im), CGImageGetHeight(im));
UIGraphicsBeginImageContextWithOptions(sz, NO, 0);
CGContextDrawImage(UIGraphicsGetCurrentContext(),
                   CGRectMake(0, 0, sz.width, sz.height), im);
CGImageRef result = [UIGraphicsGetImageFromCurrentImageContext() CGImage];
UIGraphicsEndImageContext();
return result;

}

从下面的代码

采取的帮助，以其中u会把这个代码：

UIGraphicsBeginImageContextWithOptions(CGSizeMake(leftRect.size.width, leftRect.size.height), NO, 0);
CGContextRef con = UIGraphicsGetCurrentContext();
CGContextDrawImage(con, leftRect,flip(leftReference));