How To Blur Image edges in Iphone

I have three UIImag开发者_如何学Goes added to three UIScrollviews that are positioned one under the other. I am trying to find a way to blur the adjacent edges that are between two scrollviews but am unable to find a way to do that.

Can someone please suggest a way to achieve this?

Any help will be appreciated

Thank You

Shumais Ul Haq

You could do some gaussian blurring on an image. This has been asked before.

static void blur(V2fT2f *quad, float t) // t = 1
{
    GLint tex;
    V2fT2f tmpquad[4];
    float offw = t / Input.wide;
    float offh = t / Input.high;
    int i;

    glGetIntegerv(GL_TEXTURE_BINDING_2D, &tex);

    // Three pass small blur, using rotated pattern to sample 17 texels:
    //
    // .\/.. 
    // ./\\/ 
    // \/X/\   rotated samples filter across texel corners
    // /\\/. 
    // ../\. 

    // Pass one: center nearest sample
    glVertexPointer  (2, GL_FLOAT, sizeof(V2fT2f), &quad[0].x);
    glTexCoordPointer(2, GL_FLOAT, sizeof(V2fT2f), &quad[0].s);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
    glColor4f(1.0/5, 1.0/5, 1.0/5, 1.0);
    validateTexEnv();
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    // Pass two: accumulate two rotated linear samples
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);
    for (i = 0; i < 4; i++)
    {
        tmpquad[i].x = quad[i].s + 1.5 * offw;
        tmpquad[i].y = quad[i].t + 0.5 * offh;
        tmpquad[i].s = quad[i].s - 1.5 * offw;
        tmpquad[i].t = quad[i].t - 0.5 * offh;
    }
    glTexCoordPointer(2, GL_FLOAT, sizeof(V2fT2f), &tmpquad[0].x);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glActiveTexture(GL_TEXTURE1);
    glEnable(GL_TEXTURE_2D);
    glClientActiveTexture(GL_TEXTURE1);
    glTexCoordPointer(2, GL_FLOAT, sizeof(V2fT2f), &tmpquad[0].s);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB,      GL_INTERPOLATE);
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB,         GL_TEXTURE);
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB,         GL_PREVIOUS);
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC2_RGB,         GL_PRIMARY_COLOR);
    glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_RGB,     GL_SRC_COLOR);
    glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA,    GL_REPLACE);
    glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_ALPHA,       GL_PRIMARY_COLOR);

    glColor4f(0.5, 0.5, 0.5, 2.0/5);
    validateTexEnv();
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    // Pass three: accumulate two rotated linear samples
    for (i = 0; i < 4; i++)
    {
        tmpquad[i].x = quad[i].s - 0.5 * offw;
        tmpquad[i].y = quad[i].t + 1.5 * offh;
        tmpquad[i].s = quad[i].s + 0.5 * offw;
        tmpquad[i].t = quad[i].t - 1.5 * offh;
    }
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    // Restore state
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glClientActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, Half.texID);
    glDisable(GL_TEXTURE_2D);
    glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_RGB,     GL_SRC_ALPHA);
    glActiveTexture(GL_TEXTURE0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glDisable(GL_BLEND);
}

You can use CALayer.mask to set a "mask layer" to add transparent regions. Set this on the scroll view (e.g. #import <QuartzCore/CALayer.h> ... scrollView.layer.mask = whatever) to give the edges more transparency.

I can't remember if layer masks are automatically resized. They also perform particularly poorly on older (e.g. 3G) devices. It might do what you want, though.